`12.` She asked if I did my homework right after school.

`-` Thì HTD (do) `->` Thì QKD (did) - S + V_ed + O

`-` Câu tường thuật dạng Yes or No questions 

`-` Cấu trúc: S + asked (sb) /wanted to know/... + if/whether + S + V lùi thì

`-` you `->` I, your `->` my (Chủ ngữ là she)

`13.` The girl asked the boy if he knew the way to the post office in that city. 

`-` Câu tường thuật dạng Yes or No question

`-` this `->` that (đổi trạng từ chỉ nơi chốn) 

`-` Thì HTD (know) `->` Thì QKD (knew)

`14.` The son asked the father if he would come there every weekend.

`-` Thì TLD (will come) `->` would + V-inf (would come) 

`-` Câu tường thuật dạng Yes or No question

`-` here `->` there (đổi trạng từ chỉ nơi chốn)

`15.` The teacher told Trung to do more grammar exercises to improve his English.

`-` Câu tường thuật dạng câu mệnh lệnh

`-` Cấu trúc: S + told + O + to V-inf: yêu cầu ai làm gì 

`-` your `->` his (Trung)

`16.` I asked him if he would help the poor children with their study the next year. 

`-` Thì TLD (will ... help) `->` would + V-inf (would help) 

`-` next year `->` the next year (đổi trạng từ chỉ thời gian)

`-` you `->` he (Tôi hỏi anh ấy rằng anh ấy...)

`17.` Lặp câu 12 nhưng thêm "She asked me" `->` She asked me if I did my homework right after school. 

`18.` The girl asked Tom to turn on the air-conditioner for her. 

`-` Câu tường thuật dạng câu mệnh lệnh.

`-` Cấu trúc: S + asked/told/... + O + to V-inf + O: yêu cầu ai làm gì (lịch sự)

`-` me `->` her (Chủ ngữ là The girl)

12. Đây là câu hỏi yes/no, ta dùng if.

present simple -> past simple (do -> did)

“Do you do your homework right after school?”, She asked.

-> She asked if I did my homework right after school.

13. Đây là câu hỏi yes/no, ta dùng if.

present simple -> past simple (know -> knew)

The girl said to the boy: “Do you know the way to the post office in this city?”

The girl asked the boy if he knew the way to the post office in this city. 

14. Đây là câu hỏi yes/no, ta dùng if.

present simple -> past simple (come -> came)

The son said to the father “Will you come here every weekend, dad?”

The son asked the father if he came here every weekend.

15. Đây là một câu mệnh lệnh, ta dùng told 

The teacher said: “Do more grammar exercises to improve your English, Trung”

The teacher told me to do more grammar exercises to improve my English

16. Đây là câu hỏi yes/no, ta dùng if.

present simple -> past simple (help -> helped)

next year -> the following year

I said to him “Will you help the poor children with their study next year?”

I asked If he helped the poor children with their study the following year?

17.Đây là câu hỏi yes/no, ta dùng if.

present simple -> past simple (do -> did)

“Do you do your homework right after school?”, she asked me

She asked me if I did my homework right after school.

18. Đây là một câu yêu cầu, ta dùng ask me + to + infinitive

“Would you please turn on the air-conditioner for me, Tom”, the girl said

The girl asked me to turn on the air-conditioner for her?