Answer: 30
Step-by-step explanation:
To hold a seat in the U.S. Senate, the youngest a person can be is 30 years old. However, one does not have to be 30 years old in order to run for Senate as long as they are 30 years old by the time that they are sworn in. For example, Joe Biden was 29 years old when he ran and was elected as a senator of Delaware.