сколько тебе было лет, когда ты

how old were you when you

→ сколько
phrase Rare #26,082
how old were you when you Used to ask someone's age at the time a past event happened. The phrase continues with a past-tense verb, such as научился, перестал, or покинул.
RU: Сколько тебе было лет, когда ты начал учить английский?
EN: How old were you when you started learning English?