Correct Answer - Option 1 : 907

Brothers- P, Q, R and S.

Hotel rooms numbered- 301, 302, 303 and 304.

Sum of room numbers of P and R is 603. This means room number 301 and 302 is booked by P and R, not necessarily in the same order.

The sum of room numbers of R and S is 604. This means room number 301 and 303 is booked by R and S, not necessarily in the same order.

From the above statements, it is clear that R booked room number 301, P booked room number 302 and S booked room number 303.

Therefore, room booked by Q is 304.

Sum of room numbers booked by P, Q and R = 302 + 304 + 301 = 907

Hence, option 1 is the correct answer.