Solving Equations Using
Addition and Subtraction
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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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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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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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Let’s try another example!
x ­ 6 = 10 Check
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What if we see
y + (­4) = 9 Check
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How about
­16 + z = 7 Check
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A trick question...
­n ­ 10 = 5 Check
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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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3 Examples:
1) x + 3 = 17 3) z ­ (­5) = ­13
2) 13 + y = 20
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Try these on your own...
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The answers...
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