Xét hiệu (5x + 11y) - 5(x - 2y) = 5x + 11y - (5x - 10y) = 5x + 11y - 5x + 10y = 21y

=> 5(x - 2y) = (5x+11y) - 21y

Ta có 5x+ 11y ; 21y đều chia hết cho 7 nên (5x+11y) - 21y chia hết cho 7 => 5(x - 2y) chia hết cho 7 

Mà 5; 7 nguyên tố cùng nhau => x - 2y chia hết cho 7

Vậy..

My sister likes beautiful dances in England very much.

Mark the letter A, B, C, or D on your answer sheet to indicate the sentence that is closest in meaning to each of the following questions.

You should not send money to us by post under any circumstances.

A. Under any circumstances should you not send money to us by post. 

B. Under any circumstances should not you send money to us by post. 

C. Under no circumstances should you not send money to us by post. 

D. Under no circumstances should you send money to us by post.

1.C

2.A

3.D

4.B

5.B

6.A

7.A

8.A

2 giờ đầu ng đó đi đc: 2/5 + 1/3=11/15(quãng đường)

44 km ứng với: 1- 11/15 = 4/15(quãng đường)

=>Độ dài quãng đường là:44 :4/15=165(km)