Just do length x width x height
30 + 5h = 20h
30 = 20h - 5h
30 = 15h
30/15 = h
2 = h
at 2 hrs, they both charge the same rate...
30 + 5(2) = 30 + 10 = 40
20h = 20(2) = 40
so at 2 hrs, they both charge $ 40
the formula for perimeter is l+l+w+w
So 9+9+6+6= 30 meters of fence
