Answer: Option D
$$\eqalign{
& {\text{Let}}\,{\text{Rahul's}}\,{\text{age}}\,{\text{be}}\,x\,{\text{years}}. \cr
& {\text{Then,}}\,{\text{Sachin's}}\,{\text{age}} = \left( {x - 7} \right)\,{\text{years}}. \cr
& \therefore \frac{{x - 7}}{x} = \frac{7}{9} \cr
& \Rightarrow 9x - 63 = 7x \cr
& \Rightarrow 2x = 63 \cr
& \Rightarrow x = 31.5 \cr
& {\text{Hence,}}\,{\text{Sachin's}}\,{\text{age}} \cr
& = \left( {x - 7} \right)\,{\text{years}} \cr
& = 24.5\,{\text{years}} \cr} $$