You have the following system of equations:
y = 9x - 9
y = 9
In order to solve the previous system of equations, replace y = 9 into the first equation and solve for x:
9 = 9x - 9 add 9 both sides and simplify
9 + 9 = 9x
18 = 9x divide by 9 both sides
18/9 = x
2 = x
x = 2
Hence, the solution to the system is x = 2 and y = 9.
