Answer :
line up both equations according to terms and add
-3x + 7y= -12
+ 3x + 8y=12
--------------------------------------
15y= 0
y= 0 so plug back that into either equations and get x=4
-3x + 7y= -12
+ 3x + 8y=12
--------------------------------------
15y= 0
y= 0 so plug back that into either equations and get x=4