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
