lets start with the area of the green cube b×h. 15×15=225. 225×5= 1125. I got five because there are 5 visible faces on the cube. to find the area of a triangle you use the formula 1/2 bh 9×15= 135 multiply that by 2 instead of one half because you have four triangular faces. add your areas together and you get 1395
