French phrase
Depuis combien de temps étudiez-vous ~ ?
Meaning
How long have you been studying ___?
When to use it
Asks about the length of time spent studying a subject. It is polite and suited to formal inquiries.
Example dialogue
Depuis combien de temps étudiez-vous l'informatique ?
How long have you been studying computer science?
Depuis trois ans.
For three years.