72 is the answer you are looking for here
28 tries. The ratio is 5:7, so once you multiply 5 by 4 to get 20, you do the same to 7 to get 28.
A = bh/2
2a = bh
2a/b = h
h = 2a/b
You need a ruler and a pencil. Oh and paper. Make sure that each side is equal to 4 inches. Then make a scale of 1:12, meaning 1 inch=1 foot.