Sum of 15, - 2 and 7 is​

Asphere has a diameter of 10 in. what is the volume of the sphere?

To solve the system of equations below, grace isolated the variable y in the first equation and then substituted into the second equation. what was the resulting equation? 3y=12x x^2/4+y^2/9=1

Last one and the bottom answer choice is y=(x-4)^2+1 you guys!