Answer: 500 miles
Explanation:
Given : Sergio and Lizeth have planned to rent a car from a company that charges $75 a week plus $0.25 a mile.
i.e. Fixed charge= $75
Rate per mile = $0.25
Let x denotes the number of miles.
Then, Total charges = Fixed charge+ Rate per mile x No. of miles traveled
= $75+ $0.25x
To keep budget within $200, we have following equation.

Hence, they can travel 500 miles and still keep within their $200 budget.