For shape 1, you have to divide 7.1 to get half the width of the triangle. You get 3.55 from that, and then finding the triangle itself you have to do 7.3*3.55 to get 25.915. For shape 2, you first do the harder parts (the triangles) and since there is two of them we don't need to half the width of each triangle. But first to get the width, we need to do 20-17.4=2.6. But since there are 2 triangles we need to divide that by 2 to get 1.3. Then you multiply that by 5.5 to get the final area of both triangles which is 7.15. Next you simply find the rectangle which is 17.4*5.5=95.7. You add the triangles area to get 102.85. Finally for shape 3 you simply do 7.1*20=142.
