UPSC CAPF AC 2021 Paper

(b) Let monthly incomes of A and B be 7 x and 10 x respectively and their expenditures be 2 y and 3 y respectively.

According to the question,
⇒ 7x - 2y = 1000 .......(i)
and 10x - 3y = 1000 .......(ii)
Multiplying by of Eq. (i) and by Eq (ii) and subtracting
⇒ 21x - 6y = 3000 ......(i)
⇒ 20x - 3y = 2000 .......(ii)
--- + ---
⇒ x=1000
∴ Mostly income of B = 10 × 1000 = Rs 10000