Answer: x=-5, y=9
You can use elimination to solve this system. By adding the two equations together, you get:
-x=5
Then solve for x by dividing both sides by -1:
x=-5
Now that you have x, substitute that into one of the equations to solve for y.
6(-5)+5y=15
-30+5y=15
5y=45
And now divide both sides by 5 to solve for y:
y=9