Question

How can I solve the following system of equations: -4x + y= 6, -5x -y =21. I know I can cancel out but I don't know where or where to go from there.

Answer 1

-4x + y = 6
-5x - y = 21

add both of them
-9x = 27
x = -3

(-4*-3) + y = 6
-12 + y = 6
y = 18