How i was taught how to do it was to mark the x and y in the point given. Then since a perpendicular line has an opposite reciprocal (3~-1/3). We would have to put the 3x into a -1/3 and from there just ignore the b-intercept and just put B n it should look like this (2=-1/3(-3)+b) and the solve to you’ll get y=-1/3+3. I really don’t know if it’s right i may be wrong.