$\text{1.}$ Lan said she would be very busy the next day.

$\text{→}$ I ⇒ she

$\text{→}$ will ⇒ would

$\text{→}$ tomorrow ⇒ the next day

$\text{2.}$ He said his parents were very proud of his health.

$\text{→}$ my ⇒ his

$\text{→}$ are ⇒ were

$\text{→}$ my ⇒ his

$\text{3.}$ Lien said to her brother that he ought to clean his room.

$\text{→}$ you ⇒ he

$\text{→}$ your ⇒ his

$\text{4.}$ Hoa said she visited her parents in summer.

$\text{→}$ HTD ⇒ QKD

$\text{→}$ I ⇒ she

$\text{→}$ my ⇒ her

$\text{5.}$ The students said they should finish their work.

$\text{→}$ we ⇒ they

$\text{→}$ our ⇒ their

$\text{6.}$ She said she didn't buy that book.

$\text{→}$ HTD ⇒ QKD

$\text{→}$ this ⇒ that

$\text{7.}$ The boys said they had to try their best to win the match.

$\text{→}$ we ⇒ they

$\text{→}$ must ⇒ had to

$\text{→}$ our ⇒ their

$\text{8.}$ Her mother told her she ought to wash and iron her clothes.

$\text{→}$ you ⇒ she

$\text{→}$ your ⇒ her

$\text{9.}$ Mai said her father wasn't a doctor.

$\text{→}$ my ⇒ her

$\text{→}$ isn't ⇒ wasn't

$\text{10.}$ Lan said she had to do her homework.

$\text{→}$ I ⇒ she

$\text{→}$ have to ⇒ had to

$\text{→}$ my ⇒ her

$\text{11.}$ They said they hadn't gone to school the day before.

$\text{→}$ QKD ⇒ QKHT

$\text{→}$ we ⇒ they

$\text{→}$ yesterday ⇒ the day before

$\text{12.}$ She said she had been to the cinema 2 days before.

$\text{→}$ I ⇒ she

$\text{→}$ QKD ⇒ QKHT

$\text{→}$ ago ⇒ before

$\text{13.}$ He said he was writing a test the next day.

$\text{→}$ I ⇒ he

$\text{→}$ HTTD ⇒ QKTD

$\text{→}$ tomorrow ⇒ the next day

$\text{14.}$ They said to us they would do that for us.

$\text{→}$ we ⇒ they

$\text{→}$ will ⇒ would

$\text{→}$ this ⇒ that

$\text{→}$ you ⇒ us

$\text{15.}$ She said she had learnt English for 10 years.

$\text{→}$ HTHT ⇒ QKHT

$\text{→}$ I ⇒ she

1. Lan said that she would be very busy the next day

2. He said that his parents were very proud of his health

3. Lien told her brother that he ought to clean his room

4. Hoa said that she visited her parents in summer

5. The students said that they should finish their work

6. She said that she didn't buy that book

7. The boys said that they had to try their best to win the match

8. Her mother told her she ought to wash and iron her clothes

9. Mai said that her father wasn't a doctor

10. Lan said that she had to do her homework

11. They said they hadn't go to school the day before 

12. She said she had gone to the cinema 2 days ago

13. He said he was writting a test the next day

14. They told us they would do that for us

15. She said that she had learned English for 10 years

*Statement:

S + said + (that) + S + V

S + said + to + O + (that) + S + V

S + told + O + (that) + S + V