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11-2 Solving Multi-Step Equations
 11-2 Solving Multi-Step Equations




               Warm Up
               Problem of the Day
               Lesson Presentation




Course 3 3
 Course
11-2 Solving Multi-Step Equations



    Warm Up
    Solve.

    1. 3x = 102   x = 34
        y
    2. 15 = 15 y = 225
    3. z – 100 = 21 z = 121
    4. 1.1 + 5w = 98.6 w = 19.5



Course 3
11-2 Solving Multi-Step Equations



    Problem of the Day
    Ana has twice as much money as Ben,
    and Ben has three times as much as
    Clio. Together they have $160. How
    much does each person have?
    Ana, $96; Ben, $48; Clio, $16




Course 3
11-2 Solving Multi-Step Equations




   Learn to solve multi-step equations.




Course 3
11-2 Solving Multi-Step Equations



           To solve a multi-step equation, you
           may have to simplify the equation first
           by combining like terms.




Course 3
11-2 Solving Multi-Step Equations

      Additional Example 1: Solving Equations That
                   Contain Like Terms
   Solve.
   8x + 6 + 3x – 2 = 37
            11x + 4 = 37 Combine like terms.
                – 4 – 4 Subtract 4 from both sides.
            11x     = 33
                11x = 33
                 11 11 Divide both sides by 11.
                  x=3



Course 3
11-2 Solving Multi-Step Equations

             Additional Example 1 Continued

   Check
       8x + 6 + 3x – 2 = 37
                         ?
      8(3) + 6 + 3(3) – 2 = 37   Substitute 3 for x.
                         ?
           24 + 6 + 9 – 2 = 37
                         ?
                      37 = 37 




Course 3
11-2 Solving Multi-Step Equations

               Check It Out: Example 1

   Solve.
   9x + 5 + 4x – 2 = 42
           13x + 3 = 42 Combine like terms.
               – 3 – 3 Subtract 3 from both sides.
           13x     = 39
               13x = 39 Divide both sides by 13.
               13 13
                 x=3




Course 3
11-2 Solving Multi-Step Equations

             Check It Out: Example 1 Continued

   Check
       9x + 5 + 4x – 2 = 42
                          ?
      9(3) + 5 + 4(3) – 2 = 42    Substitute 3 for x.
                          ?
           27 + 5 + 12 – 2 = 42
                           ?
                       42 = 42 




Course 3
11-2 Solving Multi-Step Equations


           If an equation contains fractions, it may
           help to multiply both sides of the
           equation by the least common
           denominator (LCD) to clear the fractions
           before you isolate the variable.




Course 3
11-2 Solving Multi-Step Equations

     Additional Example 2A: Solving Equations That
                   Contain Fractions
   Solve.
      5n+ 7= – 3
      4   4    4
           Multiply both sides by 4 to clear fractions,
           and then solve.

                (    ) ( )
               4 5n + 7 = 4 4
                   4   4
                                 –3


            4( 4)+ 4(7 )= 4( 4) Distributive Property.
              5n            –3
                     4
                    5n + 7 = –3


Course 3
11-2 Solving Multi-Step Equations

             Additional Example 2A Continued


    5n + 7 = –3
       – 7 –7 Subtract 7 from both sides.
    5n     = –10
           5n= –10   Divide both sides by 5
           5    5
           n = –2




Course 3
11-2 Solving Multi-Step Equations



       Remember!
       The least common denominator (LCD) is the
       smallest number that each of the denominators
       will divide into.




Course 3
11-2 Solving Multi-Step Equations

     Additional Example 2B: Solving Equations That
                   Contain Fractions
   Solve.
      7x + x – 17 = 2
      9    2   9    3
           The LCD is 18.

             (           ) ()
                            17           Multiply both
                 18 7x + x – 9 = 18 2    sides by 18.
                      9   2         3

  18( 9) + 18(2 ) – 18(9 ) = 18( 3)Property.
     7x       x        17        2 Distributive

                   14x + 9x – 34 = 12

                       23x – 34 = 12 Combine like terms.

Course 3
11-2 Solving Multi-Step Equations

            Additional Example 2B Continued

  23x – 34 = 12     Combine like terms.
       + 34 + 34    Add 34 to both sides.
   23x      = 46
        23x = 46    Divide both sides by 23.
        23 23
           x=2




Course 3
11-2 Solving Multi-Step Equations

            Additional Example 2B Continued
    Check
        7x + x – 17 = 2
        9     2    9     3
      7(2) (2) 17 ? 2
       9 + 2 – 9 =3        Substitute 2 for x.
          14 + 2 – 17 = 2
                      ?
          9    2    9    3
          14 + – 17 = 2?
               1
           9        9    3
          14 + 9 – 17 = 6
                      ?
           9   9    9    9 The LCD is 9.
                     6= 6
                      ?
                     9 9

Course 3
11-2 Solving Multi-Step Equations

                    Check It Out: Example 2A

   Solve.
      3n+ 5= – 1
      4   4    4
           Multiply both sides by 4 to clear fractions,
           and then solve.

                (    ) ( )
               4 3n + 5 = 4 4
                   4   4
                                 –1


            4( 4)+ 4(5 )= 4( 4)
              3n            –1
                     4                  Distributive Property.

                    3n + 5 = –1


Course 3
11-2 Solving Multi-Step Equations

            Check It Out: Example 2A Continued


    3n + 5 = –1
       – 5 –5        Subtract 5 from both sides.
    3n     = –6
           3n= –6    Divide both sides by 3.
           3    3
           n = –2




Course 3
11-2 Solving Multi-Step Equations

              Check It Out: Example 2B

   Solve.
     5x + x – 13 = 1
      9   3   9    3
      The LCD is 9.

          (     ) ()  13      1     Multiply both
           9 5x +x – 9     =9 3     sides by 9.
               9    3

      ( ) ( ) ( ) = 9(3 )
      5x       x
    9 9 +9 3 –9 9
                      13
                      1             Distributive
                                    Property.
             5x + 3x – 13 = 3

                  8x – 13 = 3 Combine like terms.

Course 3
11-2 Solving Multi-Step Equations

           Check It Out: Example 2B Continued

    8x – 13 = 3      Combine like terms.
       + 13 + 13     Add 13 to both sides.
     8x     = 16
        8x = 16
         8    8      Divide both sides by 8.
           x=2




Course 3
11-2 Solving Multi-Step Equations

           Check It Out: Example 2B Continued
    Check
        5x + x – 13 = 1
        9     3    9    3
      5(2) (2) 13 ? 1
       9 + 3 – 9 =3       Substitute 2 for x.
          10 + 2 – 13 = 1
                      ?
          9    3    9   3
          10 + 6 – 13 = 3
                      ?
           9   9    9   9 The LCD is 9.
                     3= 3
                      ?
                     9 9



Course 3
11-2 Solving Multi-Step Equations

           Additional Example 3: Travel Application

    On Monday, David rides his bicycle m miles in
    2 hours. On Tuesday, he rides three times as
    far in 5 hours. If his average speed for two
    days is 12 mi/h, how far did he ride on the
    second day? Round your answer to the nearest
    tenth of a mile.
    David’s average speed is his combined speeds for
    the two days divided by 2.

    Day 1 speed + Day 2 speed      = average speed
                2

Course 3
11-2 Solving Multi-Step Equations

                Additional Example 3 Continued


           m + 3m                       m
                             Substitute 2 for Day 1 speed
           2    5
                  = 12           3m
             2               and     for Day 2 speed.
                                  5
           m 3m
             +
 1         2    5            Multiply both sides by 2.
     2             = 2(12)
             21


           m + 3m            Multiply both sides by the
     10           = 10(24)
           2    5            LCD 10.


Course 3
11-2 Solving Multi-Step Equations

             Additional Example 3 Continued



     5m + 6m = 240        Simplify.

           11m = 240      Combine like terms. Divide
            11    11      both sides by 11.

             m ≈ 21.82

     On the second day David rode 3 times m (3m)
     or approximately 65.5 miles.


Course 3
11-2 Solving Multi-Step Equations

                Check It Out: Example 3

    On Saturday, Penelope rode her scooter m
    miles in 3 hours. On Sunday, she rides twice
    as far in 7 hours. If her average speed for two
    days is 20 mi/h, how far did she ride on
    Sunday? Round your answer to the nearest
    tenth of a mile.
    Penelope’s average speed is her combined speeds
    for the two days divided by 2.

    Day 1 speed + Day 2 speed   = average speed
                2

Course 3
11-2 Solving Multi-Step Equations

              Check It Out: Example 3 Continued


           m + 2m                       m
                             Substitute 3 for Day 1 speed
           3    7
                  = 20           2m
             2               and     for Day 2 speed.
                                  7
           m 2m
             +
 1         3    7            Multiply both sides by 2.
     2             = 2(20)
             21


           m + 2m            Multiply both sides by the
     21           = 21(40)
           3    7            LCD 21.


Course 3
11-2 Solving Multi-Step Equations

           Check It Out: Example 3 Continued



     7m + 6m = 840         Simplify.

           13m = 840       Combine like terms. Divide
            13    13       both sides by 13.

             m ≈ 64.62


      On Sunday Penelope rode 2 times m, (2m), or
      approximately 129.2 miles.

Course 3
11-2 Solving Multi-Step Equations

                        Lesson Quiz
  Solve.

  1. 6x + 3x – x + 9 = 33      x=3

  2. –9 = 5x + 21 + 3x         x = –3.75

  3.   5 + x = 33    x = 28
       8   8    8
                          9
   4. 6x – 2x = 25   x = 116
       7   21   21
  5. Linda is paid double her normal hourly rate for each
     hour she works over 40 hours in a week. Last week
     she worked 52 hours and earned $544. What is her
     hourly rate? $8.50
Course 3

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8th grade solving simple equations Practice

  • 1. 11-2 Solving Multi-Step Equations 11-2 Solving Multi-Step Equations Warm Up Problem of the Day Lesson Presentation Course 3 3 Course
  • 2. 11-2 Solving Multi-Step Equations Warm Up Solve. 1. 3x = 102 x = 34 y 2. 15 = 15 y = 225 3. z – 100 = 21 z = 121 4. 1.1 + 5w = 98.6 w = 19.5 Course 3
  • 3. 11-2 Solving Multi-Step Equations Problem of the Day Ana has twice as much money as Ben, and Ben has three times as much as Clio. Together they have $160. How much does each person have? Ana, $96; Ben, $48; Clio, $16 Course 3
  • 4. 11-2 Solving Multi-Step Equations Learn to solve multi-step equations. Course 3
  • 5. 11-2 Solving Multi-Step Equations To solve a multi-step equation, you may have to simplify the equation first by combining like terms. Course 3
  • 6. 11-2 Solving Multi-Step Equations Additional Example 1: Solving Equations That Contain Like Terms Solve. 8x + 6 + 3x – 2 = 37 11x + 4 = 37 Combine like terms. – 4 – 4 Subtract 4 from both sides. 11x = 33 11x = 33 11 11 Divide both sides by 11. x=3 Course 3
  • 7. 11-2 Solving Multi-Step Equations Additional Example 1 Continued Check 8x + 6 + 3x – 2 = 37 ? 8(3) + 6 + 3(3) – 2 = 37 Substitute 3 for x. ? 24 + 6 + 9 – 2 = 37 ? 37 = 37  Course 3
  • 8. 11-2 Solving Multi-Step Equations Check It Out: Example 1 Solve. 9x + 5 + 4x – 2 = 42 13x + 3 = 42 Combine like terms. – 3 – 3 Subtract 3 from both sides. 13x = 39 13x = 39 Divide both sides by 13. 13 13 x=3 Course 3
  • 9. 11-2 Solving Multi-Step Equations Check It Out: Example 1 Continued Check 9x + 5 + 4x – 2 = 42 ? 9(3) + 5 + 4(3) – 2 = 42 Substitute 3 for x. ? 27 + 5 + 12 – 2 = 42 ? 42 = 42  Course 3
  • 10. 11-2 Solving Multi-Step Equations If an equation contains fractions, it may help to multiply both sides of the equation by the least common denominator (LCD) to clear the fractions before you isolate the variable. Course 3
  • 11. 11-2 Solving Multi-Step Equations Additional Example 2A: Solving Equations That Contain Fractions Solve. 5n+ 7= – 3 4 4 4 Multiply both sides by 4 to clear fractions, and then solve. ( ) ( ) 4 5n + 7 = 4 4 4 4 –3 4( 4)+ 4(7 )= 4( 4) Distributive Property. 5n –3 4 5n + 7 = –3 Course 3
  • 12. 11-2 Solving Multi-Step Equations Additional Example 2A Continued 5n + 7 = –3 – 7 –7 Subtract 7 from both sides. 5n = –10 5n= –10 Divide both sides by 5 5 5 n = –2 Course 3
  • 13. 11-2 Solving Multi-Step Equations Remember! The least common denominator (LCD) is the smallest number that each of the denominators will divide into. Course 3
  • 14. 11-2 Solving Multi-Step Equations Additional Example 2B: Solving Equations That Contain Fractions Solve. 7x + x – 17 = 2 9 2 9 3 The LCD is 18. ( ) () 17 Multiply both 18 7x + x – 9 = 18 2 sides by 18. 9 2 3 18( 9) + 18(2 ) – 18(9 ) = 18( 3)Property. 7x x 17 2 Distributive 14x + 9x – 34 = 12 23x – 34 = 12 Combine like terms. Course 3
  • 15. 11-2 Solving Multi-Step Equations Additional Example 2B Continued 23x – 34 = 12 Combine like terms. + 34 + 34 Add 34 to both sides. 23x = 46 23x = 46 Divide both sides by 23. 23 23 x=2 Course 3
  • 16. 11-2 Solving Multi-Step Equations Additional Example 2B Continued Check 7x + x – 17 = 2 9 2 9 3 7(2) (2) 17 ? 2 9 + 2 – 9 =3 Substitute 2 for x. 14 + 2 – 17 = 2 ? 9 2 9 3 14 + – 17 = 2? 1 9 9 3 14 + 9 – 17 = 6 ? 9 9 9 9 The LCD is 9. 6= 6 ? 9 9 Course 3
  • 17. 11-2 Solving Multi-Step Equations Check It Out: Example 2A Solve. 3n+ 5= – 1 4 4 4 Multiply both sides by 4 to clear fractions, and then solve. ( ) ( ) 4 3n + 5 = 4 4 4 4 –1 4( 4)+ 4(5 )= 4( 4) 3n –1 4 Distributive Property. 3n + 5 = –1 Course 3
  • 18. 11-2 Solving Multi-Step Equations Check It Out: Example 2A Continued 3n + 5 = –1 – 5 –5 Subtract 5 from both sides. 3n = –6 3n= –6 Divide both sides by 3. 3 3 n = –2 Course 3
  • 19. 11-2 Solving Multi-Step Equations Check It Out: Example 2B Solve. 5x + x – 13 = 1 9 3 9 3 The LCD is 9. ( ) () 13 1 Multiply both 9 5x +x – 9 =9 3 sides by 9. 9 3 ( ) ( ) ( ) = 9(3 ) 5x x 9 9 +9 3 –9 9 13 1 Distributive Property. 5x + 3x – 13 = 3 8x – 13 = 3 Combine like terms. Course 3
  • 20. 11-2 Solving Multi-Step Equations Check It Out: Example 2B Continued 8x – 13 = 3 Combine like terms. + 13 + 13 Add 13 to both sides. 8x = 16 8x = 16 8 8 Divide both sides by 8. x=2 Course 3
  • 21. 11-2 Solving Multi-Step Equations Check It Out: Example 2B Continued Check 5x + x – 13 = 1 9 3 9 3 5(2) (2) 13 ? 1 9 + 3 – 9 =3 Substitute 2 for x. 10 + 2 – 13 = 1 ? 9 3 9 3 10 + 6 – 13 = 3 ? 9 9 9 9 The LCD is 9. 3= 3 ? 9 9 Course 3
  • 22. 11-2 Solving Multi-Step Equations Additional Example 3: Travel Application On Monday, David rides his bicycle m miles in 2 hours. On Tuesday, he rides three times as far in 5 hours. If his average speed for two days is 12 mi/h, how far did he ride on the second day? Round your answer to the nearest tenth of a mile. David’s average speed is his combined speeds for the two days divided by 2. Day 1 speed + Day 2 speed = average speed 2 Course 3
  • 23. 11-2 Solving Multi-Step Equations Additional Example 3 Continued m + 3m m Substitute 2 for Day 1 speed 2 5 = 12 3m 2 and for Day 2 speed. 5 m 3m + 1 2 5 Multiply both sides by 2. 2 = 2(12) 21 m + 3m Multiply both sides by the 10 = 10(24) 2 5 LCD 10. Course 3
  • 24. 11-2 Solving Multi-Step Equations Additional Example 3 Continued 5m + 6m = 240 Simplify. 11m = 240 Combine like terms. Divide 11 11 both sides by 11. m ≈ 21.82 On the second day David rode 3 times m (3m) or approximately 65.5 miles. Course 3
  • 25. 11-2 Solving Multi-Step Equations Check It Out: Example 3 On Saturday, Penelope rode her scooter m miles in 3 hours. On Sunday, she rides twice as far in 7 hours. If her average speed for two days is 20 mi/h, how far did she ride on Sunday? Round your answer to the nearest tenth of a mile. Penelope’s average speed is her combined speeds for the two days divided by 2. Day 1 speed + Day 2 speed = average speed 2 Course 3
  • 26. 11-2 Solving Multi-Step Equations Check It Out: Example 3 Continued m + 2m m Substitute 3 for Day 1 speed 3 7 = 20 2m 2 and for Day 2 speed. 7 m 2m + 1 3 7 Multiply both sides by 2. 2 = 2(20) 21 m + 2m Multiply both sides by the 21 = 21(40) 3 7 LCD 21. Course 3
  • 27. 11-2 Solving Multi-Step Equations Check It Out: Example 3 Continued 7m + 6m = 840 Simplify. 13m = 840 Combine like terms. Divide 13 13 both sides by 13. m ≈ 64.62 On Sunday Penelope rode 2 times m, (2m), or approximately 129.2 miles. Course 3
  • 28. 11-2 Solving Multi-Step Equations Lesson Quiz Solve. 1. 6x + 3x – x + 9 = 33 x=3 2. –9 = 5x + 21 + 3x x = –3.75 3. 5 + x = 33 x = 28 8 8 8 9 4. 6x – 2x = 25 x = 116 7 21 21 5. Linda is paid double her normal hourly rate for each hour she works over 40 hours in a week. Last week she worked 52 hours and earned $544. What is her hourly rate? $8.50 Course 3