4

số cách chọn là 

12C4 - 5C1.4C1.3C2 - 5C1.4C2.3C1- 5C2.4C1.3C1

I visit our uncle's house not only in spring but also in autummn.

theo nhớ thì sau dấu phẩy số thập phân bao nhiêu số thì số tự nhiên thêm bấy nhiều số 0 ròi chia bình thường

12.34 ÷ 2 

thì là 1234 ÷ 200 á em

13,2 km/h

13,2 km = 13 200 mét

1 giờ = 60 phút

Trong một phút đi được 13 200 ÷ 60 = 220 mét

537.8 

40......0.18

42070

25.....0.189

1.You will get overweight if you're careful with your diet.

2.Because there was a loud noise next to my door last night, Icouldn't sleep.

3.He spends his free time on looking after the garden.

4.Peter told Mary that they might go sightseeing in Sa Pa the following week.

5. It is very interesting to play beach games.

6.My mother cooks better than my sister.

5:  quý tộc, tăng lữ, thương nhân, thợ thủ công và nông dân.

56. Mrs White asked me where i was doing at that momment.

57. Mrs Brown asked me where I was living then.

58.Nick said that we could clean the beach together.

59. Mr Jones said to his children that he was so happy to hear that.

60.Nam said that the environment was severely affected by pollution.

61. The guiter can be played by him.

62. Four languages can be spoken by him.

63. The rules may be quickly forgotten.

64.The lesson should be repeatedly studied.

65.The competition must be won by my brother.

66. He was sitting on a chair which is uncomfortable.

67. She works for a company where makes toys for children. 

Hoán vị 3 bạn nữ thành 1 nhóm hàng ngang:

=> có 3! cách xếp

Hoán vị nhóm gồm 3 bạn nữ với 7 nam  là hoán vị 8 phần tử :

=-> 8 ! cách xếp

Tổng số cách xếp thỏa là : 3!.8! cách