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