Idon't get it , i really needs asap you

An architect is designing a water fountain for a park she uses the given function to model the water jet flowing from the fountain nozzles where h(x) gives the height of the water jugs in feet x feet from the starting point h(x)=-1/20x+x+15

Can any one me with the answers to these questions asap?

The square pyramid has a volume of 441 cubic inches. what is the value of x? 1/7x is the height x is the base