Substitution or elimination.
-3x+2y=23
5x+2y=-17

don't give me the answer! can you just explain a little

It's a simultaneous equation ^^; So basically I first look at the number in front of the Y values (if they aren't the same you have to multiply each equation by the other number in front of Y in the second line and vice versa but anyways) you add the two equations if they are the same so: -3x+2y=23 + 5x+2y = -17 which should give you 2x=40 then divide by two to get x put your x answer back into the top or bottom equation (your call ^^;) and then work out what must be the Y value! I really hope this helps! ^^;