Divide ₹3450 among A, B and C in the ratio 3 : 5 : 7.

Let the value of A be 3x, the value of B be 5x and the value of C be 7x.

According to the question,

$$\begin{gathered} 3x+5x+7x=3450 \\ \Rightarrow 15x=3450 \\ \Rightarrow x=\frac{3450}{15} \\ \Rightarrow x=230 \end{gathered}$$

Hence, the value of A is 3 × 230 = ₹690,
the value of B is 5 × 230 = ₹1150,
and the value of C is 7 × 230 = ₹1610.