Answer:
2
Explanation:
If we look at the graph this is an increasing graph where y increases with respect to x so in other words we can say that y is directly proportional to x.

and when we remove the proportionality sign we replace it with an equal to sign and a constant. So it becomes ,

now to find the Constant of proportionality which is k we can use any ordered pair(coordinate/point) from the graph,
Lets take ( 2 , 4) where 2 represents the value of x on the x-axis and 4 represents the value of y on the y-axis so now,

so the constant of proportionality is 2