¿Cuántos años tiene? thats how old are you, or ?que edad tienes ?
You would use the pronoun "tú" when talking to a classmate in Spanish.
compañero de clase
compañero de clase
Compañero/a del clase.
compañero: classmate, co-worker.
for denouncing a pro-Spanish classmate
Male classmate and un compañera de clase means female classmate .
Que es una compañera
ask a classmate for help
Cuántos años tiene Ud.?
It can mean classmate or colleague (for work).
To answer which age group of a set of numbers has twice as many people as another age group, I would need to see the options. The best way to find the answer if you are unsure is to ask a teacher, or a classmate.