if you notice the triangle on the left-hand-side, it has a base of 8 ft and a height/altitude of 10.
now, the triangular pyramid has 3 of those triangles standing up, and one at the base lying down, so 4 triangles with that base and altitude. So we can simply find the area of all 4 of those triangles, sum them up and that's the area of the triangular pyramid.
[tex] \bf \stackrel{\textit{area of the four triangles}}{4\left[ \cfrac{1}{2}(8)(10) \right]} [/tex]
