Hi Andrea,

"Personne n'a son billet"   --> Nobody (no-one) has their ticket/pass

The verb avoir is not being negated here, which I understand; is your concern.

What is being negated is the pronoun "personne" (Nobody or no-one) and as the subject of this sentence is written, "Personne ne" (no-one).

Hope this helps

Bonne continuation

Jim

As Jim says, he negation here is ne..personne, which means"nobody". Personne can appear also before the corresponding ne whenever it doubles as the subject of the sentence but that doesn't change its meaning in the negation. Here are some examples:

Alice a mon billet. -- Alice has my ticket.
Alice n'a pas mon billet. -- Alice doesn't have my ticket.
Personne n'a mon billet. -- Nobody has my ticket.