the answer is 400in^2
work :
you can separate this figure into two regular figures: a parallelogram and a right triangle
let's find the area of the parallelogram
(height x side)
[tex]16 \times 20 = 320[/tex]
and now we can find the area of the right triangle (height x side /2
[tex](8 \times 20) \div 2 = 160 \div 2 = 80[/tex]
so the area of the whole shape is :
[tex]320 + 80 = 400[/tex]
good luck