Let P, Q and R represent their respective monthly incomes. Then, we have: 
P + Q = (5050 x 2) = 10100 .... (i) 
Q + R = (6250 x 2) = 12500 .... (ii) 
P + R = (5200 x 2) = 10400 .... (iii) 
Adding (i), (ii) and (iii), we get:  2(P + Q + R) = 33000  or   P + Q + R = 16500 .... (iv) 
Subtracting (ii) from (iv), we get P = 4000. 
Therefore:: P's monthly income = Rs. 4000.   |