To create a linear function that models the problem described, we need to account for both the fixed rental cost and the variable cost based on the miles driven.
The rental company charges a flat fee of $50, and an additional $0.50 for each mile driven, which is represented by \( x \).
The total cost \( f(x) \) can be expressed as follows:
\[ f(x) = 0.50x + 50 \]
Thus, the correct response is:
f(x) = 0.50x + 50