If you add each like term together (so -6x + 6x, 5y + 4y, and 1 + -10)
You do this you end up with
0 + 9y = -9
9y = -9
y = -9/9
y = -1
Then substitute it back in to one of the tw equations:
6x + 4(-1) = -10
6x + -4 = -10
6x = -10 +4
6x = -6
x = -6/6
x = -1