You would plug it in, so where there is a y in the first equation you will plug in the second equation, so it would become 3x+2(x-3)=9 and then solve. First you would distribute and get 3x+2x-6=9, then combine like terms and get 5x-6=9, then add 6 to both sides and get 5x=15, then divide both sides by 5 and get x=3
