1) I haven't met him before. Have I met him before?
2) They haven't learned the new rule. Have they learned the new rule?
3) He hasn't finished his work. Has he finished his work?
4) The boy hasn't woken up. Has the boy woken up?
5) She hasn't made this mistake before. Has she made this mistake before?
6) They haven't had a long walk today. Have they had a long walk today?