1. **Problem:** Sheila has 25000 to invest and wants to earn 12000 interest at 5.8% per year. Find the time (years). 2. **Formula for simple interest:** $$I = P \times r \times t$$ where $I$ is interest, $P$ principal, $r$ rate (decimal), $t$ time (years). 3. Substitute values: $$12000 = 25000 \times 0.058 \times t$$ 4. Solve for $t$: $$t = \frac{12000}{25000 \times 0.058} = \frac{12000}{1450} \approx 8.28$$ years --- 5. **Problem:** April sold 28500 of ads and earned 1282.50 commission. Find commission rate. 6. Formula: $$\text{Commission Rate} = \frac{\text{Commission}}{\text{Total Sales}}$$ 7. Substitute: $$\text{Rate} = \frac{1282.50}{28500} = 0.045 = 4.5\%$$ --- 8. **Problem:** Find principal $P$ if interest $I$ is 183.75 at rate 3.5% per year for 21 months. 9. Convert 21 months to years: $$21 \div 12 = 1.75 \text{ years}$$ 10. Use $I = P \times r \times t$; $$183.75 = P \times 0.035 \times 1.75$$ 11. Solve for $P$: $$P = \frac{183.75}{0.035 \times 1.75} = \frac{183.75}{0.06125} = 3000$$ --- 12. **Problem:** Elleda earned 15% commission on 75900 sale. Deposited 40% of commission at 3% interest for 2 years. Find deposit and interest earned. 13. Commission: $$75900 \times 0.15 = 11385$$ 14. Deposit: $$11385 \times 0.40 = 4554$$ 15. Interest: $$I = 4554 \times 0.03 \times 2 = 273.24$$ --- 16. **Problem:** 6-piece notebook set costs 150; sales tax 6%. Find total cost. 17. Sales tax: $$150 \times 0.06 = 9$$ 18. Total cost: $$150 + 9 = 159$$ --- 19. **Problem:** Marina invested 25000 at 7.5% for 3 years. Find interest earned. 20. Interest: $$I = 25000 \times 0.075 \times 3 = 5625$$ --- 21. **Problem:** Carlito was given 7.5% commission amounting 1012.50. Find price of washing machine. 22. Let $C$ be cost: $$1012.50 = 0.075 \times C \Rightarrow C = \frac{1012.50}{0.075} = 13500$$ **Final answers:** 1) 8.28 years 2) 4.5% commission rate 3) 3000 principal 4) 4554 deposit, 273.24 interest 5) 159 total cost 6) 5625 interest 7) 13500 washing machine price