In John 8, the Jews said Jesus was not yet how old, yet claimed to have seen Abraham?

Answer: Fifty

When Jesus said Abraham rejoiced to see his day, they replied, "You are not yet fifty years old, and You have seen Abraham?"

“Your father Abraham rejoiced that he would see My day. He saw it and was glad.” Then the Jews said to Him, “You are not yet fifty years old, and You have seen Abraham?””— John 8:56-57 (BSB)