It has to have +3 because 0 alresdy starts at 3 than use any point (I choose (5,9)) and find how much changed. The point moved 6 up and 5 to the right so divide 6/5 and get 1.2. Then test it with other points. (2,5.4) is a great example because it shows that whatever the equation is it is not 1.5 or anything above.
