This shape is just a rectagle with triangles ontop.
Lets work out the rectangle first. 12 x 9 = 108.
Now the triangles. The area for traingle is 1/2 base x height so 2 x 12 = 24 / 2 = 12. So each triangle is 12 ft ^2. You have 2 so it is 24.
24 + 108 =132 ft^2
keep ur crown