Exercise 59 Page 316

p=- 20

Practice makes perfect

To solve the equation, we have to isolate p on one side. Using the Subtraction Property of Equality, we will subtract 9 from both sides of the equation. This will eliminate the addition and isolate p.

9+p=- 11

LHS-9=RHS-9

9+p-9=- 11-9

Subtract terms

p=- 20

To check that this solution is correct, substitute p=- 20 into the original equation and simplify.

9+p=-11

p= - 20

9+( - 20) ? = -11

a+(- b)=a-b

9-20 ? = -11

Subtract term

- 11 = - 11 ✓

Since the left-hand side and right-hand side are equal, p=- 20 is the correct solution.

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