1. **State the problem:** A store owner discounted birthday cards from $1 to $0.58. We need to find the discount as a percentage. 2. **Formula for discount percentage:** $$\text{Discount Percentage} = \left(\frac{\text{Original Price} - \text{Discounted Price}}{\text{Original Price}}\right) \times 100\%$$ 3. **Calculate the discount amount:** $$1 - 0.58 = 0.42$$ 4. **Calculate the discount percentage:** $$\frac{0.42}{1} \times 100\% = 42\%$$ 5. **Interpretation:** The discount is 42%, meaning the price was reduced by 42% from the original price. **Final answer:** 42%