1. **Stating the problem:** We have a car priced at 1800 rials initially, and after two years, its price decreases to 1600 rials. We need to find the percentage decrease in price. 2. **Formula used:** The percentage decrease is calculated by the formula: $$\text{Percentage Decrease} = \frac{\text{Original Price} - \text{New Price}}{\text{Original Price}} \times 100$$ 3. **Applying the values:** Original Price = 1800 New Price = 1600 4. **Calculate the difference:** $$1800 - 1600 = 200$$ 5. **Calculate the percentage decrease:** $$\frac{200}{1800} \times 100 = \frac{200 \times 100}{1800} = \frac{20000}{1800} \approx 11.11$$ 6. **Conclusion:** The price of the car decreased by approximately 11.11%.