Since the x terms have opposite terms we can just add the two equations together...
3x+y-3x+4y=27-42
5y=-15 then divide both side by 5
y=-3, and use either original equation to solve for x, 3x+y=27 becomes:
3x-3=27
3x=30
x=10 so the solution to the system of equations is the point:
(10, -3)
