1. **State the problem:** We have a group of people categorized by their mode of transportation: car only, bicycle only, both car and bicycle, and neither. 2. **Given data:** - People who go by car only: 280 - People who go by both car and bicycle: 140 - People who go by bicycle only: 220 - People who go by neither: 160 3. **Find:** The probability that a randomly selected person uses only car or only bicycle. 4. **Total number of people:** $$\text{Total} = 280 + 140 + 220 + 160 = 800$$ 5. **Number of people who use only car or only bicycle:** $$280 + 220 = 500$$ 6. **Probability formula:** $$P(\text{only car or only bicycle}) = \frac{\text{Number of people who use only car or only bicycle}}{\text{Total number of people}}$$ 7. **Calculate the probability:** $$P = \frac{500}{800}$$ 8. **Simplify the fraction:** $$P = \frac{\cancel{500}^{\times 100}}{\cancel{800}^{\times 160}} = \frac{5}{8}$$ 9. **Final answer:** The probability that a randomly selected person uses only car or only bicycle is **$\frac{5}{8}$** or 0.625.