1. Reported speech:

Phương pháp giải:

Câu tường thuật luôn luôn phải lùi thì, VD như: 
HTĐ => QKĐ
HTHT => QKHT
QKĐ => QKHT
HTTD => QKTD
QKTD => QKHTTD
Must => Had to
Will => Would

Lời giải chi tiết:

1. My friend said that they had moved into their new flat.
2. The teacher said that Japan was a densely populated city.
3. He said that his parents had already seen that film.
4. He told me that he knew exactly what she had done the day before.
5. He said that his sister was working then.
6. Tony said to me that he would me with those exercises the following day.
7. She told me that she had been waiting for the bus whwen he had arrived.
8. She said that she hadn't gone to the party.
9. They said that they had to see those movies that night.
10. My father told Ben that he was sure he had seen Ben there the previous week.

=>
1. My friend said that they had moved into their new flat.
2. The teacher said that Japan was a densely populated city.
3. He said that his parents had already seen that film.
4. He told me that he knew exactly what she had done the day before.
5. He said that his sister was working then.
6. Tony said to me that he would me with those exercises the following day.
7. She told me that she had been waiting for the bus whwen he had arrived.
8. She said that she hadn't gone to the party.
9. They said that they had to see those movies that night.
10. My father told Ben that he was sure he had seen Ben there the previous week.
Câu tường thuật -> lùi thì
HTĐ -> QKĐ
HTHT -> QKHT
QKĐ -> QKHT
HTTD -> QKTD
QKTD -> QKHTTD
Must -> Had to
Will -> Would