(x-3)^2+x(x+9) simplify the expression

If x = 12 and y = 3, what is the value of x - y 2? 81 6 3 18

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

How do you use the elimination method for this question? explain, because i really want to understand!