Vì 1 cái bàn đắt hơn 1 cái ghế 30 000 đồng => 7 cái bàn đắt hơn 3 cái ghế: 30 000 . 4 = 120 000 (đồng)

7 cái bàn giá: (510 000 + 120 000) : 2 = 315 000 (đồng)

1 cái bàn giá: 315 000 : 7 = 45 000 (đồng)

3 cái ghế giá: 510 000 - 315 000 = 295 000 (đồng)

1 cái ghế giá: 295 000 : 3 = ...

Suppy the correct tense of the verbs in the brackets.
1. It's 8 o'clock. I (stay) ....am staying.... at home. I (play) ....am playing.... games with my friends my brother (read) ....is reading.... a book in his room.
2. How many books does your library (have) ....have....?
- It (have) ....has.... a lot, about one thousand.
3. Nam (go) ....goes.... to the library every day. He (like) ....likes.... reading books, but he (not like) ....doesn't like.... biology and history books.
4. Is your brother (make) ....making.... so much noise in your room?
5. I (see) ....am going to see.... a movie tomorrow. Will you (go) ....go.... with me?
6. How do I (find) ....find.... a book in the library?
7. What do your sister and you usually (do) ....do.... in the evening?
- I usually (watch) ....watch.... TV and she (do) ....does.... her homework.
8. My sister (practise) ....practises....the piano in the club three times a week.
9. In my country, there (be) ....are.... no lessons on Saturday.
10. I (give) ....am going to give.... the farewell party next month.

Chúc bạn học tốt :D