Take either equation and solve for either variable. Then take the expression equal to that variable and substitute it for the variable in the other equation.
Let's solve for x in the second equation:
Now substitute in first equation:
Collect the y terms and add 12 to both sides:
Divide both sides by -11:
y = -3
Now that we know y we can substitute it to find x:
So the solution to the system of equations is the point (0,-3).