1. The problem is to understand what percentages are and how to calculate them. 2. A percentage represents a part out of 100. For example, 25% means 25 out of 100. 3. To convert a percentage to a decimal, divide by 100. For example, 25% = \frac{25}{100} = 0.25. 4. To find a percentage of a number, multiply the number by the decimal form of the percentage. For example, to find 25% of 80, calculate 80 \times 0.25 = 20. 5. To convert a decimal to a percentage, multiply by 100. For example, 0.75 \times 100 = 75%. 6. To increase a number by a percentage, multiply the number by (1 + decimal percentage). For example, increasing 100 by 20%: 100 \times (1 + 0.20) = 120. 7. To decrease a number by a percentage, multiply the number by (1 - decimal percentage). For example, decreasing 100 by 20%: 100 \times (1 - 0.20) = 80. This covers the basics of percentages and how to work with them.