1. **Stating the problem:** Convert the given percentages into decimals. 2. **Formula:** To convert a percentage to a decimal, divide the percentage value by 100. 3. **Explanation:** Since percent means "per hundred," dividing by 100 shifts the decimal point two places to the left. 4. **Calculations:** (a) $90\% = \frac{90}{100} = 0.90$ (b) $58.35\% = \frac{58.35}{100} = 0.5835$ (c) $224\% = \frac{224}{100} = 2.24$ 5. **Final answers:** (a) 0.90 (b) 0.5835 (c) 2.24