Well it gives you the height of each face of the figure (4 inches) and the base (2 inches)
The formula for the surface area is simply to add up the area of each face. Each triangle is 1/2bh, but there are 4 congruent triangles, so you should multiply this formula by 4 to get 2bh. b = 2 and h = 4. Plug in the values and simplify, so you get 2(2)(4), or 16 square inches.
The area of the square face on the bottom is simply length by width (2(2)), which is 4 square inches. Add the values, and your final answer is 20 square inches