The ratio between the present ages of Raj & Ravi is 3:7, respectively. After 4 years, Ravi's age will be 39 years. What was Raj's age 4 years ago?

Let present ages of Raj and Rani are $3x$ and $7x$ year respectively.
According to question,

$$\begin{gathered} 7x+4=39 \\ \Rightarrow 7x=39-4=35 \\ \Rightarrow x=5 \end{gathered}$$
Hence, Raj's age 4 years ago
$$\begin{gathered} =3x-4=3\times 5-4 \\ =11 years \end{gathered}$$