can someone check this your brother tú your teacher Ud. your best friend tú your friend’s mother Ud. your elderly neighbor Ud. your principal Ud. your new acquaintance who is your age tú

yes it's right

Explanation:

generlly speaking tu is used with people younger than or acquaintances/people that are close to you. While Ud. is used for the elderly and for people you show respect to    

answerestan corriendo; i believe this is correct, plz check first good luck;