check the picture below.
now the base has an area of 64 ft², as shown on the picture a 8x8 base, the total surface area, meaning the triangular faces area plus the base, we know is 224 ft².
well, what's the area of the triangular faces anyway? well, if we just subtract hte base from the total surface area, what we're left with, is the lateral area, namely the area of the triangular faces only, 224 - 64.
now, there are four equal triangular faces, divide that by 4, and that's the area of one of them, (224 - 64) / 4.
