Find the area of the shaded polygons:

Check the picture below.

now, notice, is really just a large triangle in red, with a base of 4 and a height of 3 units, and two smaller triangles below it, one has a base 1 and a height of 1, and the other has a base of 3 and a height of 1.

so just get the area of each, sum them up, and that's the shaded area.