Chapter 13 - Probability - 13-1 Experimental and Theoretical Probability - Practice and Problem-Solving Exercises - Page 828: 23

$\frac{12}{65}$

To calculate probability, we need to divide the number of chances for a certain outcome to occur by the total number of outcomes. In this case, there are $12$ cars that are red, and $65$ in total. When we divide $12$ by $65$, we get $\frac{12}{65}$, which is the experimental probability a car is red, or $P(\text{red})$.