It's my bag
bag is mine.
Если существительное, которое тебе/кому-нибудь принадлежит стоит перед местоимением, то местоимение меняем: my-mine, her-hers и т.д.
1. Is this his book?
2. It's (their) door, not / ours ).
3. They're new pupils and I don't know (their names.
4. (Му flаt is bigger than his), but / his) is nicer.
5. That's not (my CD. (Му is new.
6. We took (their / skateboards and they took (our ).
7. Is this pencil case hers)?
8. Is this (his house or (her ?