Let d represent the number of days Andrew can afford to rent while staying within his budget.​
Let m represent the number of miles driven
We were told that the rental car company charges $30 per day to rent a car and $0.12 for every mile driven.The cost for d days would be $30d. The total cost for d days would be
0.12m + 30d
Given that he has at most $150 to spend, it means that the amount he needs to spend is less than or equal to $150
The inequality representing this scenario would be

This means that the number of days is 3 because it cannot be a fraction. It is not up to 4 days