Answer-How many boxes are placed between Y and R?

Only five boxes are placed between J and L. Q is placed immediate above L. Only three boxes are placed between Q and P. Following 5 cases are possible Number of boxes placed between J and P is same as between K and Q. Not less than four boxes are placed between Q and R. One box is placed between R and W. Box Y is placed above box X. All the cases except Case3 eliminate as they do not satisfy the third hint. Thus the final arrangement is as follows