The volume of any right prisim is given by [tex] V = A_b \times h [/tex] where [tex]A_b[/tex] is the area of the base and [tex]h[/tex] is the height.
In this case, the base is a triangle and so its area can be found thus:
[tex] A = \frac{1}{2} b \times h [/tex]
So:
[tex]V= A_b \times h_p [/tex]
[tex]V=(\frac{1}{2} \times {b} \times h_b) \times h_p[/tex]
[tex]V=(\frac{1}{2} \times {5cm} \times 8cm) \times 7cm[/tex]
[tex]V=20cm^{2} \times 7cm [/tex]
[tex]V=140cm^{3}[/tex]
