Multiplying the second equation by 4/3 and adding it to the first, we get 36=9x and by dividing both sides by 9, we get x=4. Next, we can plug that into the second equation (it doesn't matter which equation) to get 3*4-3y=18=12-3y. Subtracting 12 from both sides, we get 6=-3y and by dividing both sides by -3 we get y=-2