Explanation:

To find the single equivalent discount, we use the formula for successive discounts:

1. Formula: To find two successive discounts, take the formula:

$$ \text{Effective Discount} = a + b - \left(\frac{a \times b}{100}\right) $$

where \(a\) is the first discount (12.5%) and \(b\) is the second discount (20%).

2. Calculation:

- Effective Discount = 12.5% + 20% - \(\frac{12.5 \times 20}{100}\)

- = 32.5% - 2.5%

- = 30%

3. Comparison and Evaluation:

- Option 1: 28% - Below calculated effective discount.

- Option 2: 27.5% - Below calculated effective discount.

- Option 3: 30% - Matches calculated effective discount.

- Option 4: 31.5% - Above calculated effective discount.