Exercise 9 Page 141

To solve an equation, we should first gather all of the variable terms on one side and all of the constant terms on the other side using the Properties of Equality. In this case, the only variable terms are already on the right-hand side of the equation, so we will start by combining them.

- 8=1.3m -2.1m

SubTerm

Subtract term

- 8=- 0.8m

DivEqn

.LHS /(- 0.8).=.RHS /(- 0.8).

- 8/- 0.8 = - 0.8m/- 0.8

DivNegNeg

- a/- b=a/b

8/0.8 = 0.8m/0.8

CalcQuot

Calculate quotient

10=m

RearrangeEqn

Rearrange equation

m=10

The solution to the equation is m=10. We can check our solution by substituting it into the original equation.

- 8=1.3m -2.1m

Substitute

m= 10

- 8 ? = 1.3( 10) -2.1m( 10)

Multiply

Multiply

- 8 ? = 13-21

SubTerm

Subtract term

- 8 =- 8

Since the left-hand side is equal to the right-hand side, our solution is correct.