at the age of ～ (～歳で): She started playing the piano at the age of 5. (彼女は5歳でピアノを始めました。) - 試験に出る! 英単語検索辞書

at the age of ～ (～歳で): She started playing the piano at the age of 5. (彼女は5歳でピアノを始めました。)

She started playing the piano at the age of 5.