The ages of Samina and Suhana are in the ratio of 7 : 3 respectively. After 6 years, the ratio of their ages will be 5 : 3. What is the difference in their ages?

Answer: Option B

Let Samina's age be 7x years.
Then, Suhana's age = 3x years
$$\begin{array}{rl}& \therefore \frac{7x+6}{3x+6}=\frac{5}{3}\\ & \Rightarrow 3\left(7x+6\right)=5\left(3x+6\right)\\ & \Rightarrow 21x+18=15x+30\\ & \Rightarrow 6x+12\\ & \Rightarrow x=2\end{array}$$
Difference in their ages = (7x - 3x) years
= 4x years
= (4 × 2) years
= 8 years