1. **State the problem:** Piper wants to rent a car for $d$ days, driving 350 miles, with a budget of at most 140. 2. **Write the inequality:** The total cost is the daily charge plus the mileage charge: $$28d + 0.08 \times 350 \leq 140$$ 3. **Calculate the mileage cost:** $$0.08 \times 350 = 28$$ 4. **Substitute and simplify:** $$28d + 28 \leq 140$$ 5. **Isolate $d$:** $$28d \leq 140 - 28$$ $$28d \leq 112$$ 6. **Divide both sides by 28:** $$\cancel{28}d \leq \frac{112}{\cancel{28}}$$ $$d \leq 4$$ 7. **Interpretation:** Piper can afford to rent the car for at most 4 days to stay within her budget. **Final answer:** $$d \leq 4$$