First group the coefficients together on their side of the equal sign.
-x + 3x = 2x.
Then, since it is a positive number, subtract it from that side and the other side.
On the other side, the x becomes -x.
Add the 6 from the other side to the 8 to make 14.
14 = -x
Divide both sides by -1, to get the answer.
x = -14
