This is how I chose to do this: Split the shape into three: a rectangle and two triangles. Then find the area of each. Rectangle: 12 x 6 = 72 Triangles (if you take both triangles, you can make a square, that's what I'm doing): 18 - 12 = 6; 6 x 6 = 36 Add the two to get the complete area: 72 + 36 = 108 Your answer will be 108 feet³.