Answer: 72 cubic feet
Explanation:
Given : Mr.Addison is building a sandbox shaped like a rectangular prism.
Then , the dimension of sandbox (l w h) is given by :-
8 feet long, 6 feet wide, and 1.5 feet deep.
We know that the volume of rectangular prism is given by :-

Then , the volume of sandbox is given by :-

Hence, the volume of sandbox = 72 cubic feet