First break it up into 3 different rectangles based on what you know. Since you can make two big 4*8 rectangles, do so first.
2(4*8)=64
The middle rectangle comes next. You can figure out that height by subtracting the 3s from the total 8. So the height = 8-(3+3) = 2.
2*4=8
64+8= 72
