Breakdown of Вы живёте в квартире девять?
вы
you (plural or formal)
квартира
apartment
жить
to live
в
in / to (direction)
Questions & Answers about Вы живёте в квартире девять?
Why do we use the basic number девять (nine) here instead of saying 'the ninth apartment'?
Just like in English, Russian often uses basic counting numbers (cardinal numbers) as names or labels for things like apartments, buses, or rooms. Saying в квартире девять (in apartment nine) is perfectly natural and more common than using the word for 'ninth'.
Since квартире is in the Prepositional case, shouldn't the number девять change its ending too?
Not in this situation! When a number is just acting as a name or label placed after the noun (like 'apartment nine'), it stays frozen in its basic dictionary form. You only worry about changing the ending of the noun before it.
Why is it в квартире and not в квартира?
The preposition в (in) followed by a location triggers the Prepositional case. For most feminine nouns ending in -а like квартира (apartment), you drop the -а and add -е, making it квартире.
How do you form a 'Do you...' question in Russian without a word for 'Do'?
Russian doesn't use helper words like 'do' or 'does' to make questions. To turn the statement Вы живёте в квартире девять (You live in apartment nine) into a question, you simply keep the exact same word order and raise the pitch of your voice on the most important word (usually the number here) when speaking.