The ratio of weekly income of A and B is 9 : 7 and the the ratio of their expenditure is 4 : 3. If each saves Rs. 200 per week, then the sum of their weekly income is = ?

	A	:	B
Income	9	:	7
Expense	4	:	3

Income - Savings + Expenditure
$$\eqalign{ & \therefore \frac{{9x - 200}}{{7x - 200}} = \frac{4}{3} \cr & \Rightarrow 27x - 600 = 28x - 800 \cr & \Rightarrow x = 200 \cr & {\text{Sum of weekly income}} \cr & = 9x + 7x = 16x \cr & = 16 \times 200 = {\text{Rs}}.\,3200 \cr} $$