Answer:
3/4
Step-by-step explanation:
Constant of Proportionality is just a fancy way of saying slope (for a line passing through (0, 0), at least).
You can find it by looking at y/x, which will be equal at any point on the line (which is why it is a "constant").
So, for multiple points on the line:
1.5 / 2 = 3/4
3 / 4 = 3/4
4.5 / 6 = 3/4
