Make the shape into two polygons. A rectangle and a triangle. Find the area of the rectangle by multiplying lxw. 14x18=252 Then find the area of the triangle A=l x w/2 20-14=6 18-11=7 6 x 7 = 42 42/2=21 252+21=273 273/5 is about 54 He can fit 54 chickens.