Answer:
Use tú for informal situations such as with a friend, children, young people, people you know very well. Use usted (Ud.) for formal situations such as in a job interview, in a bank, with elderly people, with someone you don't know or you have just met
Explanation:
Tú tienes ochenta y un años (The second phrase)
Answer:
El botones le dió una tabla de surf a Miguel.
It would be, ¿Cuántos años tienes?
The tu form of tener is tienes
