First, you need to find the height, in which it says “a height that’s half the length of the longer base side. Can you guess what that is between 7 and 5? It is 7. And you would find half of that which is 3.5. Now you know the height is 3.5. The formula to find a rectangular pyramid's volume is lwh/3 which you would do 7 * 5 * 3.5, which is equal to 122.5, and then you would divide that by 3, which is 40.833 which would round to 40.8, so there is your answer.
It is 40.8 units^3
