Arectangular prism has a height of 12 cm and a square base with sides measuring 5 cm. a pyramid with the same base and the height of the prism is placed inside the prism. what is the volume of the space outside the pyramid but inside the prism?

The answer is 200 cm³

The volume of the rectangular prism (V1) is:
V1 = l · w · h                       (l - length,  w - width,  h - height)
It is given:
h = 12 cm
w = l = 5 cm (since it has a square base which all sides are the same size).
Thus: V1 = 12 · 5 · 5 = 300 cm³

The volume of pyramid (V2) is:
V2 = 1/3 · l · w · h                   (l - length,  w - width,  h - height)
It is given:
h = 12 cm
w = l = 5 cm (since it has a square base which all sides are the same size).
V2 = 1/3 · 12 · 5 · 5 = 1/3 · 300 = 100 cm³

The volume of the space outside the pyramid but inside the prism (V) is a difference between the volume of the rectangular prism (V1) and the volume of the pyramid (V2): 
V = V1 - V2 = 300 cm³ - 100 cm³ = 200 cm³