12. To find the area of a triangular prism use the formulas for a prism and for a triangle. To find area of the triangle, do 1/2base*height. 1/2(8*6)=24 Now multiply by the length of the prism to find the volume. 24*3=72. 13. 150/ (7*8) = 2.68 14. 1/2x^3