The monthly incomes of A and B are in the ratio 3 : 4 and the ratio of their monthly expenditures is 2 : 3. If each saves ₹4000 per month, then what is the income of B?

₹16000

                   A  :  B

Incomes       3  :  4

Expenditure  2  :  3

              _________

              -4000  -4000 

Using the cross - multiplication method, 

9r - 8r = (-4000 x 2) - (-4000 x 3)

       r  = 4000

Income of B = 4 x 4000 = ₹16000