1. **State the problem:** A store pays 18 for a teapot and marks up the price by 40%. We need to find the amount of the mark-up. 2. **Formula:** The mark-up amount is calculated by multiplying the original price by the mark-up percentage. $$\text{Mark-up} = \text{Original Price} \times \text{Mark-up Percentage}$$ 3. **Apply the values:** $$\text{Mark-up} = 18 \times 0.40$$ 4. **Calculate:** $$\text{Mark-up} = 7.2$$ 5. **Interpretation:** The amount of the mark-up is 7.2. So, the store adds 7.2 to the original price as the mark-up.