Question

Solve the system of equations 3x – 3y = 30 and 2x + y = 11 by combining the equations.

Answer 1

Times bottom equation by 3 and top by 2 to get the same coefficient of x
6x-6y=60
6x+3y=33
Minus the bottom by the top
-9y=27
y=-3
substitute this in to one of the equations
2x -3 = 11
add 3 to both sides
2x=14
x=7