Since you can't have a negative y in a y = mx + b equation you have to make it postive. You also have to do everything you do on one side to the other. To do this you have to multiply everything by -1. This will make everything positive b/c it cancels out the other negative. (Two negatives equals a positive) You should be left with y = 6x + 3. The -1 cancelled the -y, -6x, and -3 so you add 3 instead of subtract it.
