P = 2(L + W)
P = 28
L = 2W - 1
28 = 2(2W - 1 + W)
28 = 2(3W - 1)
28 = 6W - 2
28 + 2 = 6W
30 = 6W
30/6 = W
5 = W ....width is 5 ft
L = 2W - 1
L = 2(5) - 1
L = 10 - 1
L = 9 <=== length is 9 ft
Well it boils down to 18 - (4 + 9) which is 18 - 13 or 5. So the answer is 5 in this equation.
I believe is 70 multiply 1400 times 5% and it will give you 70