To find the length of the rectangle, you need to first do 20 x 2 = 40 because when you finding the perimeter you have to do W + L + W + L = P (or Wx2 + Lx2 = P). You then subtract 40 from 68 (68 - 40) where you get 28 left. you then just divide 28/2 and you get 14. I may be way off but that's how I learned it.
