Big Ideas Math: Modeling Real Life, Grade 7
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1. Solving Equations Using Addition or Subtraction
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Exercise 22 Page 131

Use the Addition Property of Equality to eliminate the subtraction.

d=- 5.9

Practice makes perfect
To solve the equation, we have to isolate d on one side. Using the Addition Property of Equality, we will add 3.4 to both sides of the equation. This will eliminate the subtraction and isolate d.
- 9.3 = d - 3.4
- 9.3 + 3.4 = d - 3.4 + 3.4
- 5.9 = d
d = - 5.9
To check that this solution is correct, let's substitute d=- 5.9 into the original equation and simplify.
- 9.3 = d - 3.4
- 9.3 ? = - 5.9 - 3.4
- 9.3 = - 9.3 âś“
Since the left-hand side and right-hand side are equal, d=- 5.9 is the correct solution.