The constant of proportionality is basically just the slope, so the answer is 1/6.
Step-by-step explanation:
Count how many Y units it goes up to get the the black point from (0,0) (the origin). You go up 1 unit to go 6 units to the right meaning the slope is 1/6.
That is the rise over run technique and there are many others, such as point slope form, and y2-y1 over x2-x1.
