Final answer:
When providing rescue breathing to an adult victim, the first aider should give one breath every 5 seconds.
Step-by-step explanation:
When providing rescue breathing to an adult victim, the first aider should give one breath about one every 5 seconds. This is based on the recommended guidelines for CPR (Cardiopulmonary Resuscitation) provided by organizations like the American Heart Association. Giving one breath every 5 seconds helps maintain oxygen supply to the victim's lungs and can increase the chances of survival. It is crucial to avoid giving breaths too quickly as this can raise the pressure in the chest and decrease blood return to the heart.