To find the constant of proportionality, put the chart numbers into this form-
y=kx
k is the constant of proportionality.
y and x are found in the chart.
2=3k
/3 /3
k=2/3
4=6k
/6 /6
k=4/6=2/3
6=9k
/9 /9
k=6/9=2/3
2/3 is the constant of proportionality, or k.
So the answer is 2/3.
Hope this helped :)