check the picture below.
keeping in mind that the right-hand-side edge is 4yards, meaning 12 feet.
since the prism is really just two triangles with a base of 6 and height of 8, and a 8x12 rectangle and a 6x12 rectangle and a 10x12 rectangle, we simply can get the area of each and sum them up, and that's the surface area of the triangular prism.
[tex]\bf \stackrel{\textit{two triangles}}{2\left[ \cfrac{1}{2}(6)(8) \right]}~~+~~\stackrel{\textit{left rectangle}}{(6\cdot 12)}~~+~~\stackrel{\textit{back rectangle}}{(10\cdot 12)}~~+~~\stackrel{\textit{right rectangle}}{(8\cdot 12)}[/tex]
