you have to cancel either your x or your y. i would cancel your y right now. you need them to be oposites. so you times the first eqaution by 3 and the second -one by 2. this will get you 72x+6y-156=0 and 12x-6y+72=0. your x will cancel if you add them together. you will get 84x-84. divde by 84 to isolate your x and x=-1. so put -1 into eother original equations and find the value of y. 6(-1)-3y=-36
-6-3y=-36
-3y=-39
y=13
then put them both back into the eqatuion to check.
6(-1)-3(13)=-36
-6-39=-36
-45/=-36
so i got it wrong but i hope that gives you the general sense of what to do