Not saying I want to. Asking for my friend

No sane teacher would ever agree. Any teacher dating a student is likely to wind up in jail.

How old are you? How old is you teacher?

Absolutely not! It doesn't matter what age the teacher and the student are. It's always wrong and always unprofessional.

how old are you? how old is you teacher?

Doesn't matter. There is no situation where it is appropriate for a teacher to have a relationship with a student of theirs.

The only time such a relationship might be appropriate is if the teacher is not a teacher of the student and they are both adults.

There have been some TV News programs about a teacher (more than one) having an affair and/or date with a student. The teacher was fired, and also charged because the student was a minor.
I would suggest that a student not even think about asking out a teacher.