Amit was given an increment of 20% on his salary.

Let $R s x$ be Amit's old salary.

His salary after increment will be Rs $\left(x+\frac{20}{100} x\right)$

According to the question, we have:

$\Rightarrow x+\frac{20}{100} x=30600$

$\Rightarrow \frac{100 x+20 x}{100}=30600 \quad(\mathrm{LCM}=100)$

$\Rightarrow \frac{120 x}{100}=30600$

$\Rightarrow 120 x=30600 \times 100$

$\Rightarrow x=\frac{30600 \times 100}{120}$

$\Rightarrow x=25500$

$\therefore$ The old salary is Rs 25500