Answer:
31.35d + 0.15(275) </= 280
Explanation:
(Daily cost x number of days) + (mileage cost x number of miles) is less than or equal to $280.
If they ask you to solve it next:
31.35d + 0.15(275) </= 280
31.35d + 41.25 </= 280
31.35d </= 238.75
d </= 7.615629998
Round it down to 7 full days
LMK if you have questions