The length of a rectangle is 12 in. more than its width. the perimeter is 64 in. determine the length of the rectangle in inches.

P = 2(L+W)
L = 12+W
P = 64 inches
64 = 2(12+W+W)
64 = 2(12+2W)
64 = 24+4W
64-24 = 4W
40 = 4W
W = 10 inches
L = 12+W
L = 12+10
L = 22 inches

The formula to use in determining the perimeter of a rectangle is:
2L + 2W = P
In this problem, we let x be the width and the length be x + 12.
2 (x + 12) + 2x = 64 in
2x + 24 + 2x = 64 in
4x + 24 = 64 in
4x = 64 in - 24 in
4x = 40 in
x = 10 in
The determine the length,
10 + 12 = 22 inches