Well first we need to keep in mind that parallel lines have the same slope. So the slope of the line we are trying to find will have the same slope as. Y-3x=6.
So we need to find the slope of that line first. To do that you will want to we need to solve Y-3x=6 for y.
To do this we add 3x to both sides thus canceling it on the left hand side of the equation. This leaves us with y=-3x+6. Now using y=la+b Where m is the slope we see that the slope is -3. So the line your looking for will have a slope of -3.
