UPSC CDS 2 2019 Math Paper

Let Rs x be the income of A,
Rs y be the income of B.
Rs 600 is the saving per month from both A and B.
Therefore expenditure of A =(x−600)
Expenditure of B =(y−600)
From given conditions, x∕y=4∕3
3x=4y
3x−4y=0.....(1)
The ratio of expenditures will be
(x−600)∕(y−600)=3∕2
Cross multiplying and simplifying we get
2x−3y=−600......(2)
Solving equations 1 and 2
We get x=2400 and y=1800
Hence monthly income of A = ₹ 2400
Monthly income of B =₹1800