The length of a rectangle is 8 in. more than its width. The perimeter is 52 in. What is the length of the rectangle?

Let length be L and W be width.  Then we have two equations:

L = W + 8   and

2*L + 2*W = 52

 

Replace L in the second equation using the first equation:

2*(W + 8) + 2*W = 52

So

4*W + 16 = 52

4*W = 36

W = 9

 

So L = 9 + 8

L = 17 inches