Answer:

Explanation:
We have been given that the variables y and x have a proportional relationship, therefore, we can represent the relationship between x and y as:
, where k is proportionality constant.
Let us substitute x=3 and y=15 in above equation to find the value of k.


Now let us substitute k=5 and y=4 in our proportionality equation to find the corresponding value of x.



Therefore, the value of x will be 0.8, when y equals to 4.