1. **State the problem:** We need to solve percent problems using equations involving the numbers 4%, 18, 240, and 42. 2. **Formula used:** The general formula for percent problems is $$\text{Part} = \text{Percent} \times \text{Whole}$$ where Percent is written as a decimal. 3. **Example problem:** Find 4% of 240. 4. **Convert percent to decimal:** $$4\% = \frac{4}{100} = 0.04$$ 5. **Set up the equation:** $$\text{Part} = 0.04 \times 240$$ 6. **Calculate:** $$\text{Part} = 9.6$$ 7. **Interpretation:** 4% of 240 is 9.6. 8. **Another example:** What percent of 42 is 18? 9. **Set up equation:** Let $x$ be the percent as a decimal. $$18 = x \times 42$$ 10. **Solve for $x$:** $$x = \frac{18}{42}$$ 11. **Simplify fraction:** $$x = \frac{\cancel{18}}{\cancel{42}} = \frac{3}{7} \approx 0.4286$$ 12. **Convert to percent:** $$0.4286 \times 100 = 42.86\%$$ 13. **Interpretation:** 18 is 42.86% of 42. 14. **Summary:** Use the formula $$\text{Part} = \text{Percent} \times \text{Whole}$$ and convert percents to decimals to solve these problems.