To model the total cost of the shuttle in relation to the number of miles, we can break down the cost structure:
- The base fare is $15.
- The cost per mile is $0.50.
If \( x \) represents the number of miles, then the total cost \( y \) can be expressed as:
\[ y = 15 + 0.5x \]
This means that for each mile (represented by \( x \)), you add $0.50 to the initial $15 charge.
Therefore, the correct equation from the provided options is:
y = 0.5x + 15, where \( x \) is the number of miles and \( y \) is the total cost of the shuttle.