Add x to both sides of the first equation. This makes 2y=6+x. Then Multiply it all by 3. This makes 6y=18+3x. Then multiply both sides by -1. This makes -6y=-18-3x. Then combine the two equations. 6y+ (-6y)=0, x+(-3x)=-2x, and 18+(-18)= 0. This leaves 0y=-2x+0, in other words, -2x=0 Then you can divide out the -2x from both sides. 0 divided by anything is 0. This leaves x=0