French phrase
Combien de personnes y a-t-il ~ ?
Meaning
How many people are there in ___?
When to use it
Asks how many people are in a particular place. Polite and suitable in most situations.
Example dialogue
Combien de personnes y a-t-il dans la salle ?
How many people are there in the room?
Il y a quinze personnes.
There are fifteen people.