Answer:
It is:
86387.13241
Step-by-step explanation:
Find the cube root of 125. ∛125 = 5. Each side length will be 5 inches.
Check the picture below.
so, if we get the whole area of the figure, which will be the combined areas of those three rectangles, and if we get the area of the triangle, and then subtract that area from of the triangle from the whole figure's area, we're in effect making a whole in the total area, and what's leftover is the shaded area.

3n^2 sqrt 5n
hope that helped (: