Concept:
Successive discounts are applied one after the other on the remaining value. If the list price is $L$, the first discount is $d_1\%$, and the second is $d_2\%$, the final price $S$ is calculated as:
\[ S = L \times \left(1 - \frac{d_1}{100}\right) \times \left(1 - \frac{d_2}{100}\right) \]
Step 1: Calculate the price after the first discount.
Let the price after the first discount be $P$. We know that after a 12.5% discount on $P$, the final price is ₹1050.
\[ P \times \left(1 - \frac{12.5}{100}\right) = 1050 \]
\[ P \times \left(\frac{87.5}{100}\right) = 1050 \]
\[ P = \frac{1050 \times 100}{87.5} = \frac{105000}{87.5} = ₹1200 \]
Step 2: Calculate the first discount percentage.
The list price was ₹1500 and it was reduced to ₹1200 after the first discount.
Amount of first discount $= 1500 - 1200 = ₹300$.
\[ \text{First Discount \%} = \left(\frac{300}{1500}\right) \times 100 = \frac{1}{5} \times 100 = 20\% \]