Answer:
0.20 or 20%
Explanation:
We already know that (assuming we aren't counting a car that has seats in the truck area) there are five possible spots to sit in: the driver's seat, the front passenger (famously known as "shotgun"), middle/back left passenger, middle/back right passenger, and middle/back middle passenger.
By dividing 1 from 5 (1/5) you get a 20% chance of sitting in shotgun.
So, not that high, but its better than nothing.
Hope this helped!
Source(s) used: G*ogle Calculator