The easiest way to do this would be to use elimination method. Basically you are combining the equations. So...
3x = 36 - 15y
+11x = -78 +15y
(Add everything together)
------------------------
14x = -42
Divide.
x = -3
Now that you have the x-value you need to plug it into one of the equations. So I'm going to choose the first equation and I'm going to replace x with -3.
3x = 36 - 15y
3(-3) = 36 - 15y
-9 = 36 - 15y
Isolate the variable by subtracting 36 from both sides.
-45 = -15y
Divide.
3 = y
So your solution would be (-3, 3).
I hope this helps love! :)
