At an uncontrolled intersection, when must the car on the right yield to the car on the left?

the car on the right should yield to the car that arrived first. That is When the car on the left arrives first

Explanation:

It must be noted that the law did not grant the 'right-of-way'. The law only says when the right of way must be yielded. The law does state who must yield the right of way neither does the law give right of way to anyone.

Yielding the right of way to another vehicle simply means that you are letting them go before you in a traffic situation.

Therefore, When two vehicles approaches an intersection without no traffic signs or signals, (that is, an uncontrolled intersection) the two vehicles must slow down. Always Yield to vehicles already in the uncontrolled intersection and drivers who arrive at the uncontrolled intersection before you.

The vehicle on the left should always yield to the right of the way to the vehicle on the right. The driver with ''right-of-way'' must pay attention to avoid a collision.