Final answer:
An examination-permit driver over 21 must practice supervised driving for a specific period, commonly several months, with at least 6 months often required. Local DMV guidelines should be consulted for exact requirements.
Step-by-step explanation:
The question pertains to the requirements for an examination-permit driver over the age of 21 who is practicing supervised driving. While specific requirements can vary by state, it's commonly required that an examination-permit driver practice for a certain duration to gain the experience necessary for safe driving. As the duration can differ, a general rule is that a new driver should practice supervised driving for several months. For example, some states require at least 6 months of supervised driving practice.
It's important for the permit holder to consult their local Department of Motor Vehicles (DMV) or equivalent authority for the specific requirements in their area. Additionally, during this practice period, permit holders should be accompanied by a licensed adult driver and should focus on gaining experience in a variety of driving conditions and environments.