Chapter 3 - Solving Inequalities - 3-3 Solving Inequalities Using Multiplication or Division - Practice and Problem-Solving Exercises - Page 183: 67

6 inches

$w=l-3$ $18=2l+2w$ $18=2l+2(l-3)$ $18=2l+2l-6$ $18+6=2l+2l-6+6$ $24=4l$ $\frac{24}{4}=\frac{4l}{4}$ $6=l$ Let's check: $w=6-3$ $w=3$ $18=2\times6+2\times3$ $18=12+6$ $18=18$ The width of the rectangle is 3 inches, the perimeter is 18 inches, and the length (what we are solving for) is 6 inches.