`c oo uu`

`3x-7=x-7`

`=> 3x-x=7-7`

`=> 2x=0`

`=> x=0:2`

`=> x=0`

`1` `was` `being` `repaired`

`2` `would` `go`

`3` `had` `already` `bought`

Here are the correct forms of the verbs in parentheses in the appropriate tenses:

1. Be quiet! The baby **is sleeping**.
2. The sun **sets** in the west.
3. Mr Green always **goes** to work by bus.
4. It **does not rain** in the dry season.
5. They **are having** lunch in the cafeteria now.
6. My little sister **drinks** milk every day.
7. The doctor sometimes **returns** home late.
8. He **is writing** a long novel at present.
9. Look! The bus **is coming**.
10. The earth **moves** around the sun.
11. Sometimes it **smells** good in the kitchen now.
12. His uncle **taught** English in our school five years ago.
13. The old man **fell** as he **was getting** into the bus.
14. When I saw him, he **was sitting** asleep in a chair.
15. There **was** a lot of noise at the fair yesterday.
16. It **took** me 5 minutes to walk to school last year.
17. They **have not spoken** to each other since they quarreled.
18. I **have been trying** to learn English for years, but I **have not succeeded** yet.
19. I **have not seen** her since last week.
20. John **has already done** his homework.

`8/3` giờ

8100 : 25 = 324

Đúng vì 9x9=9+9+9+9+9+9+9+9+9=81