Final answer:
If you receive a counterfeit $20 bill, you should report it to the authorities or your bank. Be aware of the security features on currency to identify counterfeit bills.
Step-by-step explanation:
If you notice that one of the $20 bills you received is counterfeit, you should take the counterfeit bill and report it to the authorities or your bank. Counterfeit money is illegal to possess and passing it on to others is a crime.
It's important to be aware of the security features on currency notes to identify counterfeit bills. In the case of US currency, you can check for features such as the watermark, security thread, color-shifting ink, and raised printing.
Remember, it's best to handle the situation responsibly and report any counterfeit money you come across to the appropriate authorities.