3x + y = 20
x + y = 12
Subtract the bottom equation from the top one and get:
2x = 8
Divide both sides of the equation by 2 and get x = 4
Solve for y by substituting 4 in
x + y = 12 which is:
4 + y = 12
Subtract 4 from both sides of the equation and get y = 8.
The answer is x = 4, y = 8
or (4,8)
