1. Lan has long hair.

2. Nam goes to school by bike.

3. Does your family has 4 people ?

4. Nga is the tallest one in her class.

5. What about going swimming ?

6. The post office is in front of my house.

7. Milk is her favourite drink.

8. Ba is Lan's brother.

9. How high is the Mount Everest ?

10. He is a strong boy.

1. aren't I

2. doesn't he

3. do you

4. did you

B

1. B

2. B

3. D

4. B

5. D

6. B

7. A

8. D

9. D

- Oxit bazo: `BaO` (Bari oxit).

- Oxit axit: `SO_3` (Lưu huỳnh trioxit), `SO_2` (lưu huỳnh đioxit).

- Bazo: `Fe(OH)_2` (sắt II hidroxit), `NaOH` (natri hidroxit).

- Axit: `HNO_3` (Axit nitric), `HCl` (Axit clohidric).

- Muối: `K_2SO_4` (Kali sunfat), `KHCO_3` (Kali hiđrocacbonat), `NaSO_4` (Natri sunfat).

- Vâng.

- Đúng chưa ạ ?

a) `1/3 - 1/4 : 2/5 = 1/3 - 5/8 = -7/24`

b) `6/7-(5/6+1/3)-(2/3+1/7) = 6/7-5/6-1/3-2/3-1/7`

`=(6/7-1/7)-(1/3+2/3)-5/6`

`=5/7-1-5/6`

`=-47/42`

c) `-5/9 . 2/5 + 4 5/9 + 5/9 . (-3/5)`

`= -5/9 . 2/5 + 4 + 5/9 + (-5/9) . 3/5`

`=-5/9 . (2/5 + 3/5-1) + 4`

`=-5/9 . 0 +4`

`=4`

d) 3 1/2 - (5 4/7 - 1 1/2) : 0,75`

`=7/2 - (39/7 - 3/2) : 3/4`

`= 7/2 - 57/14 : 3/4`

`=7/2 - 38/7`

`=-27/14`