Substitute formula for length for the length in perimeter formula 10 = 2*4/W + 2*W 10 = 8/W + 2*W 5 = 4/W + W 5W = 4 + W^2 0 = 4 - 5W + W^2 W^2 -5W + 4 = 0 You now have a standard quadratic equation with A=1, B=-5, and C=4 Using the quadratic formula you get two possible answers W = 1, or W = 4 Let's check them Width = 1, L = 4/1 = 4 Width = 4, L = 4/4 = 1 Both make the same 1x4 rectangle. And the perimeter is 2*1 + 2*4 = 2+8 = 10