Let the salary of A be \( A \) and the salary of B be \( B \).
Given:
\[
A + B = 81,000
\]
Also, A spends 80% of his salary, so his savings are 20% of his salary, i.e., \( 0.20A \).
B spends 70% of his salary, so his savings are 30% of his salary, i.e., \( 0.30B \).
The ratio of their savings is given as 4:3:
\[
\frac{0.20A}{0.30B} = \frac{4}{3}
\]
Simplifying:
\[
\frac{2A}{3B} = \frac{4}{3} \quad \Rightarrow \quad 2A = 4B \quad \Rightarrow \quad A = 2B
\]
Substitute \( A = 2B \) into the equation \( A + B = 81,000 \):
\[
2B + B = 81,000 \quad \Rightarrow \quad 3B = 81,000 \quad \Rightarrow \quad B = 27,000
\]
Thus, the salary of B is ₹ 27,000.