The incomes of A and B are in the ratio 3 : 4, and their expenditures are in the ratio 9 : 5. If the income of A is equal to three times the expenditure of B, then what is the ratio of the savings of A and B?

Let the income of A and B is 3x and 4x respectively

Let the expenditure of A and B is 9y and 5y respectively

The saving of A and B is = (3x - 9y) and (4x - 5y) respectively........(i)

Given , 

Income of A = 3 times the expenditure of B 

i.e; 3x = $$3\times\ 5y$$

$$\frac{x}{y\ }=\ \frac{5}{1}$$

Putting the value of x and y in equation (i)

Saving of A = $$\left(3\times5\right)-9\times1=\ 6\ $$

Saving of B = $$\left(4\times\ 5\right)-5\times1=\ 15\ $$

Required ratio = 6 : 15 

i.e; 2 : 5

Hence, Option A is correct.