Explanation:

For P- Q x R ÷ S, on the basis of the information given in the question,

R is the daughter of S and Q is the sister of R.

Therefore, Q is also daughter of S, and P is the son of Q.

Thus, P is the son of Q, who is daughter of S.

Hence, P is related as daughter's son to S.

Hence option 3 is the correct answer.