A positive relationship. The reason being y=3x represents the overall slope of the equation, as well as the point (3,9) and (5,15) are the outcomes of the equation. For instance when you start at the origin with the equation you move up 3 and move to the right 1 this is the same with (3,9) and (5,15) just continuing the pattern with these points.
(e.g: (1,3), (2,6), (3,9), (4,12), (5,15).)