1. Let's state the problem: A person bought a product for $100 and sold it for $80. What is the loss in terms of amount and percentage? 2. Calculate the loss amount: $$\text{Loss} = \text{Cost Price} - \text{Selling Price} = 100 - 80 = 20$$ 3. Calculate the loss percentage using the formula: $$\text{Loss Percentage} = \left(\frac{\text{Loss}}{\text{Cost Price}}\right) \times 100 = \left(\frac{20}{100}\right) \times 100 = 20\%$$ 4. Therefore, the person incurred a loss of $20 which is 20% of the cost price.