How to ask age in Japanese and vietnamese

NAN SAI DESUKA。Bạn bao nhiêu tuổi – how old are you?

Or oikusudesuka

何歳ですか

おいくつですか

Yonjusai 40 years old 四十歳

三十歳 30years old

NAN SAI desu ka how old are you

Watashi wa ni ju go SAI desu

何歳ですか。私は三十さいです