Start by converting your two equations into slope-intercept form.
3x - 3y = -9
-3y = -3x -9 Subtract 3x from both sides
y = x +3 Divide both sides by -3
2x + y = 9
y = -2x + 9 Subtract 2x from both sides.
Then graph both lines (in which case the point where they intersect is the solution) or substitute in each point until both equations are true.
In this case the solution is (2,5); both equations become 5=5 when you substitute in the point's coordinates.
