Cả 3 câu là dạng câu tường thuật.

27.The teacher tells us to learn harder and harder.(tell sb+to V:bảo ai làm gì)

28.My mother says that we were having a party the next day.(are having->were having/tomorow->the next day/the following day)

29.I say to him that our teacher would come on time.(will->would)

27,The teacher tells us to learn harder and harder 

28,My mother says that they were having a party the next day 

29,I say to him that their teacher would come on time 

#good_luck