okay so. im not good at explaining. but ill try my best
you go with your basic X over Y soooo 2X you would go up 2 because its a positive number. and to the.. left 3 becuse it - if it was a + you would go to the right 3 but sense its -3y you go to the left
so fare your going to go from the -9 point on your graph up 2 over 3
and if its just Y ots over 1
i really hope this makes sence and helps