Number of chocolates = x
Number of tokens = y
Proportional equation:
y = kx
Where:
k: constant of proportionality
By looking at the graph, we can see that there is a coordinate point (x,y), which is (5,10)
Replace x, y by the coordinate point from the graph and solve for k:
10= 5k
10/5= k
2= k
Constant of propotionality : 2