To find the side length of a square, you have to divide the perimeter by 4 (since a square has 4 sides). 28 divided by 4 is 7 and 20 divided by 4 is 5. to find the area of each square, you have to multiply each side length by two. 7 times 7 is 49 and 5 times 5 is 25. 49 minus 25 is 24.
