Luckily for us, the diagram already divided this figure into separate polygons. What I will be explaining is basically the addition of the areas of all the separate polygons. The area of the uppermost triangle is:
1/2 x b x h
= 1/2 x 20 x 8
(the base is 20, because in a parallelogram, opposite sides are congruent)
=10 x 8
= 80 in. squared
The next polygon we will be taking the area of is the parallelogram with the base length of 20 and the height of 16.
Area = b x h
= 20 x 16
= 320 in. squared
Now all we have left to do is add the two areas to obtain the total area.
Total Area = 320 + 80 = 400 in. squared