UPSC NDA Math Model Paper 8

Monthly income of (A + B) = 2 x 7760 = 15,520 .... (1)
Monthly income of (B + C) = 2 x 10990 = 21,980 .... (2)
Monthly income of (C + A) = 2 x 9070 = 18,140 .... (3)
Adding the above equations, we get :
2(A + B + C) = 15,520 + 21,980 + 18,140 = 55,640
∴ A + B + C = 27, 820 .... (4)
Subtracting equation (4) - (3), we get
(A + B + C) - (C + A) = 27, 820 - 18, 140 = 9680
So, Monthly income of B = 9680
Now,
Annual salary of B = 12 x 9680 = Rs 1,16,160