The answer is 8cm.
Firstly, we need to find the volume of the first prism, by doing 5 x 9 x 10 = 450cm^3.
Because we know the volume of the second prism is also 450cm^3, we need to divide this by 7.5 to get 60. Because the base is a square, we divide 60 by 7.5 to get the final height of 8cm.
