If 9x+2y^2−3z^2=132 and 9y+2y^2−3z^2=−12, then x−y = (a) 3 (b) 8 (c) 16 (d) 120 (e) 144

(C) 16

Step-by-step explanation:

Subtract the second equation from the first equation.

9x + 2y^2 - 3z^2 = 132 minus 9y + 2y^2 - 3z^2 = -12

                            9x + 2y^2 - 3z^2 = 132

                            -(9y + 2y^2 - 3z^2 = -12 )  

This will change all the signs of the second equation.

9x + 2y^2 - 3z^2 = 132

-9y - 2y^2 + 3z^2 = +12

You have left 9x - 9y = 144.

Factor out the 9 so you have 9(x - y) = 144

Divide both sides by 9

x - y = 16