In order for two lines to be parallel, they have to have the same slope (m) so we already know that the question is: y= -3x + b
In order to find b, we need to plug in the coordinate (-4,6) into the x and y and solve.
6= -3(-4) + b
6= 12 + b
-6 = b
This then means that the equation is y= -3x-6
