to find the surface area of a figure, you find the area of each side and add it together
so the triangular shape would be
.5(6) * 8 = 24
.5(14) * 8 = 56
14 * 12 = 168
then you add 168 + 56 + 56 + 24 + 24 = 328
the surface area of the triangular shape is 328
the surface area of the rectangular prism
29 * 21 = 609
35 * 29 = 1015
21 * 35 = 735
735 + 735 + 1015 + 1015 + 609 + 609 = 3808
therefor the rectangular prism has a greatest surface area than the triangular shape because 3808 is greater than 328