Question 261618
For this problem, it is telling you the value of y.  So simply plug that in where the y is and then solve for x.

2x - 6 = 5x + 15  So what I would do is subtract 5x from each side to get:
-3x - 6 = 15  Now we can add six to both sides, to get rid of the negative 6.
-3x = 21  Now, to get x by itself, we need to divide each side by -3.  

-3/-3 =1  We want 1x (or simply, x) on the left.   On the right, 21/-3 = -7

So x = -7