Need to find shaded area of figure please help!

39 ft^2

Step-by-step explanation:

Find the area of the triangle and subtract the area of the square.

area of triangle = bh/2

area of square = s^2

shaded area = bh/2 - s^2

shaded area = (20 ft)(16 ft)/2 - (11 ft)^2

shaded area = 160 ft^2 - 121 ft^2

shaded area = 39 ft^2