If I'm asking "How are you?" to a singular person in a formal way, why to I say "Как Ваши дела" instead of "Как Ваш дела"? Does "Как Ваш дела" mean anything?
2 Answers
We use Ваши because it is for the plural дела. The whole phrase is in the Nominative case, just like, for example, мои друзья (мои друзья здесь), твои книги (твои книги интересные), Ваши столы (Ваши столы красивые) etc.
When we ask somebody about how something/someone is, we use the Nominative:
Как ваши друзья? - Хорошо.
Как твой проект? - Плохо. BUT Как твои проекты? - Плохо.
Как Ваши дела? - Отлично.
"Как Ваш дела" is ungrammatical.
Does "Как Ваш дела" mean anything?
No, it's a mistake. The pronoun should be in the plural because it refers to the plural noun дела. Ваши is a polite form and it can be used addressing one person and a group as well. If you know a person well you can say
Как твои дела?
There are also informal greetings avoiding the addressee (we don't say possessive pronouns as often as they are used in English)
Как дела? Как жизнь? Как оно ничего?(joking) Что новенького?