Final answer:
At a four-way stop, the vehicle on the right has the right of way when three vehicles reach it simultaneously.
Step-by-step explanation:
When three vehicles reach a four-way stop at the same time, the vehicle on the right has the right of way. This means that the driver of the vehicle on the right should proceed first, followed by the driver on the left, and finally the driver in the middle. If all three vehicles arrive at the intersection simultaneously, it is important for the drivers to communicate and determine who should go first in order to ensure a safe and smooth flow of traffic.