What is the variance of the data set?

Astudent simplified a rational expression as shown.

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

Hi my sisters and brothers can tell me the answer because i don’t understand the question