1) It is cold, isn't it?
2) Здесь ошибка, правильное окончание - am I?
3) You aren't a student, are you?
4) I am not 13, am I?
5) It was windy, was it?
6) They were soldiers, weren't they?
7) Learn English and speak, won't you?
8) You willn't be a doctor, will you?