Explanation:
the surface area of that object consists of
2 triangles (one left, one right)
1 rectangle at the top
1 rectangle at the bottom
1 rectangle in the back
so, we need to calculate the area of each of these 5 areas and sum them up. that's it.
the area of such a triangle is
6×8/2 = 24 m²
we have 2 such triangles, so in total they are 48 m².
the rectangle at the top
10×12 = 120 m²
the rectangle at the bottom
12×8 = 96 m²
the rectangle in the back
12×6 = 72 m²
so the total surface area is
48 + 120 + 96 + 72 = 336 m²