1. How long was your flihgt from Hongkong to Hanoi?

=> How long did it take you to fly from Hongkong to Hanoi?

2. My mother can cook very well.

=>My mother is a good cook

3. Roller-skating doesn’t interest me.

=> I am not interested in Roller-Skating.

4. Why were you absent from class last Monday?

=> Why didn't you come/go to class last Monday?

5. I didn’t have a toothache. They didn’t have a toothache.

=>  I didn't have a tootache and they didn't, either.

1.How long did it take you to fly from HongKong to Ha Noi ? 

- take sb time to do sth : ai đó mất bao nhiêu thời gian để làm gì

- Did + S + V nguyên + O ? 

2.My mother is a very good cook 

- cook (n,v) : đầu bếp , nấu

- S + be + (a/an) + adj + N 

- S+V + adv

3.I am not interested in roller-skating

- be interested in +N/V-ing : hứng thú ở cái gì/việc gì

4.Why didn't you go to class last Monday ? 

- absent from : vắng mặt

- Did + S + V nguyên + O ? 

5. I didn't have a toothache and they didn't either

- Câu đồng tình với câu phủ định 

- Neither + be/Aux + S

- S + be/aux + not + either