To model the relationship between the number of miles (x) and the total cost of the shuttle (y), we start with the information given:
The cost is $15 plus $0.50 per mile. This can be expressed with the equation:
\[ y = 0.5x + 15 \]
Where:
- \( y \) is the total cost of the shuttle.
- \( x \) is the number of miles.
So the correct response is:
y = 0.5x + 15, where x is the number of miles and y is the total cost of the shuttle.