Exercise 13 Page 8

r=18, see solution.

Practice makes perfect

To solve the given equation for r, we first need to rewrite the addition of the negative term as a subtraction.

r+(- 8)=10

a+(- b)=a-b

r-8=10

Now, we will add 8 to both sides of the equation to isolate r. We want to add 8 because addition and subtraction are inverse operations — they cancel each other out. This is allowed by the Addition Property of Equality.

r-8=10

AddEqn

LHS+8=RHS+8

r-8+8=10+8

AddTerms

Add terms

r=18

We will check our solution by substituting this result back into the original equation and simplifying. If doing so results in an identity, our solution is correct.

r+(- 8)=10

Substitute

r= 18

18+(- 8)? =10

AddNeg

a+(- b)=a-b

18-8? =10

SubTerms

Subtract terms

10=10 ✓

Since substituting r=18 resulted in an identity, our solution is correct.