check the picture below.
so, notice, the prism is really just 6 rectangles stacked up to each other at the edges. So if we just get the area of each rectangle and sum them up, that's the surface area of the prism.
left and right, two 6x5 rectangles
top and bottom, two 17x5 rectangles
front and back, two 17x6 rectangles
[tex]\bf \stackrel{\textit{left and right}}{(6\cdot 5)}~~+~~\stackrel{\textit{top and bottom}}{(17\cdot 5)}~~+~~\stackrel{\textit{front and back}}{(17\cdot 6)}[/tex]
