Aniin endaso-biboonagiziyan? - How old are you? (=how so many years old are you?)
Aniin endaso-biboonagizid? - How old is he?
The vai verb biboonagizi is used to tell how old a person (or something alive) is. Preverbs expressing numbers are used with it:
Ningo-biboonagizi - He is one year old.
Niningo-biboonagiz - I am one year old.
Niizho-biboonagizi - He is two years old.
Giniizho-biboonagiz - You are two years old.
Niso-biboonagizi - He is three years old.
Niiyo-biboonagiziwag - They are four years old.
Midaaso-biboonagizi - He is ten years old.
To express numbers larger than twenty daso-biboonagizi ('so many yeas old') is placed after numerals sometimes. As it is with clock time expressions there is more that one way to say how old a person is:
Niishwaswi-shi-niizh daso-biboonagizi - He is twenty two years old.
Niishwaso-biboonagizi ashi-niizh - He is twenty two years old.
Niishwaswi-shi-niizh nindaso-biboonagiz - I am twenty two years old.
Saying 'when sombody is/was/will be ... years old', particle apii or pii (when) is usually used:
mii dash apii midaaso-biboonagiziyaan, mii aw animoons gii-mikawag.
and when I [was] ten years old, I found that puppy.
For more examples of age expressions see also Of the age from Familiar phrases to facilitate conversation in the Indian language.