so for a triangular prism, its volume is just the area of the triangular face times its height.
now, notice the picture below, so the triangle has a base of 9 and a height of 4.
[tex] \bf \stackrel{\textit{area of triangle}}{\cfrac{1}{2}(9)(4)}
~~\cdot ~~\stackrel{height}{7}\implies 18\cdot 7\implies 126 [/tex]
