This document discusses how to solve equations using addition and subtraction properties of equality. It explains that to solve an equation means to isolate the variable on one side. It then introduces the addition property of equality, which states that if a = b, then a + c = b + c, meaning any number can be added to both sides of an equation without changing whether it is true. Several examples are worked through to demonstrate adding and subtracting various numbers from both sides of an equation. Finally, the subtraction property of equality is presented similarly.

1. Solving Equations Using
Addition and Subtraction
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2. To Solve an Equation means...
• To isolate the variable on
one side of the equation.
• Ex: x = 5 is solved for x.
• y = 2x ­ 1 is solved for y.
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3. Addition Property of Equality
if a = b, then a + c = b + c.
What it means:
You can add any number to BOTH sides of an
equation and the equation will still hold true.
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4. An easy example:
We all know that 7 = 7.
Does 7 + 4 = 7? NO!
But 7 + 4 = 7 + 4.
The equation is still
true if we add 4
to both sides.
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5. Let’s try another example!
x ­ 6 = 10 Check
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6. What if we see
y + (­4) = 9 Check
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7. How about
­16 + z = 7 Check
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8. A trick question...
­n ­ 10 = 5 Check
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9. Subtraction Property of Equality
if a = b, then a - c = b - c.
What it means:
You can subtract any number from BOTH sides of an
equation and the equation will still hold true.
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10. 3 Examples:
1) x + 3 = 17 3) z ­ (­5) = ­13
2) 13 + y = 20
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12. Try these on your own...
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13. The answers...
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