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Check the picture below.
so, to get the area of the triangles, we can simply run a perpendicular line from the top to the base, and end up with a right-triangle with a base of 22 and a hypotenuse of 34, let's find the altitude.

so then the surface area of the triangular prism is,
3n = 1/81; divide both sides by 3 to isolate n:
3n/3 = 1/81 divided by 3. Remember that when you divide, you use the reciprocal and multiply instead!!
n = 1/81(1/3) = 1/243. Now plug 1/243 back in for n, and 3/243 is equivalent to 1/81