Answer: The number of miles would be no more than 350 miles.

Step-by-step explanation:

Let the number of days be ‘d’.

Let number of miles be ‘m’.

Cost of each day = $75

Cost of each mile = $0.50

Total amount must be no more than $400.

According to question, it becomes,

75d+0.50mleq 400

Since the number of days = 3

So, we put the value of days in the above equation:

75times 3+0.50mleq 400\\225+0.50mleq 400\\0.50mleq 400-225\\0.50mleq 175\\mleq dfrac{175}{0.50}\\mleq 350

Hence, the number of miles would be no more than 350 miles.