Answer:
9 x 20ft = 180
If one of those values 8ft and 20ft is the diagonal then we deduct the square of thise numbers being √400 - √81 = √309 and find √309 square of 17.57ft
17.57 x 9 = 158.13
so √158.12 = 12.57
and √162 = 12.72
But your question was just a case of finding how to do area and for that we use L x W to find area
A = 9 x 20 = 180ft^2
Explanation: