the area of shaded region = area of big circle - area of small circle
area of big circle = pi x r x r
r = 32
3.14 x 32 x 32
=3215.36ft square
area of small circle = pi x r x r
=3.14 x 20 x 20
=1256ft square
= 3215.36 - 1256
=1959.36ft square
= 1959ft square