That's a trapezoid,
[tex]A = \frac 1 2 (b+B)h[/tex]
[tex]A = \frac 1 2 (4+12) 4 = 32[/tex]
Answer: 32
But say we didn't know the formula. We can chop out the 4 by 4 square and we have two 45/45/90 triangles side 4 left over, so two 4 by 4 squares,
A = 2(4)(4) = 32
We can think of this as 12 by 4 rectangle with two 4 by 4 right triangles chopped out:
A = 12(4) - 2(1/2)(4)(4) = 48 - 16 = 32
