CPM Homework Help : GB8I Problem 6-12

Solve this problem by writing and solving an equation. Be sure to define your variable. Does your answer make sense in this context?

A rectangle has a perimeter of $30$ inches. Its length is one less than three times its width. What are the length and the width of the rectangle?

Step 1:

Set up two equations:
$3W − 1 = L$
$2W + 2L = 30$

Step 2:

Substitute $\left(3W − 1\right)$ for $L$ and solve the equation:
$2W + 2 \left(3W − 1\right) = 30$

Answer:

Width is $4$ inches and length is $11$ inches.