Để một số chia hết cho 3, tổng các chữ số của số đó cũng phải chia hết cho 3. 

Để số 2a + 9 chia hết cho 3, ta cần số 2a phải chia hết cho 3, tức là a phải là số chia hết cho 3. Các số từ 0 đến 9 chia hết cho 3 là 0, 3, 6, 9.

Vậy có 4 chữ số a thoả mãn điều kiện a31a5 chia hết cho 3.

\(#HaAnn\)

Bạn nào thấy sai thì chỉ mình nhaa, mình cảm ơn ạaa~~

[Không biết mình làm có đúng không ạ!]

1- London is visited by thousands of people every year.

2- The thief is arrested by police cars.

3- CO2 is absorbed by trees.

4- Photos are taken by Jane.

5- A lot of waste is produced by people.

6- The animals are fed by the farmers.

7- Films are watched by Mr. Jones.

8- English is spoken by the people.

9- Comics are read by him.

10- Volleyball is played by us.

11- The song is sung by them.

12- Photos are taken by me.

13- Poems are written by the writer.

14- The children are helped by the police.

15- The flowers are watered by mother.

16- The car is washed by my husband.

17- Halloween is loved by people around the world.

18- Blue shoes are worn by the teachers.

19- The school is cleaned by the janitor.

20- The house is cleaned by my mother everyday.

It was difficult but I opened the box. I saw a letter inside out and ..read. it carefully. When I looked ........at...... the address and date, I couldn't believe your home is so far away! And you hid the box in the forest 30 year ...ago.. I am very happy that I have found a new friends ...who... lives in city in another.

@Bùi Quỳnh Anh

Với mỗi câu trả lời tham khảo bạn phải ghi rõ chữ TK (tham khảo) bên trên bài làm của mình. 

Cảm ơn bạn nhiều ạ!

@Minh Vương

Câu trl tham khảo cuả bạn k hề liên quan đến câu hỏi, bạn chú ý!

Mình sẽ hỏi vì sao em đó khóc và tìm cách dỗ em bé.

kurumi trả lời trước Chi nhé!

Lần sau nếu copy nhớ ghi TK nhaa, còn vc trl thì chúng mik cx cứ tự nhiên th chứ đừng tranh chấp nhaaa^^

My summer holiday started in May. I and my family go to Da Nang. I get up early and go to the train. Then, I and my family took a taxi to my grandparent's house. It's really fantastic! In the morning, I get up late and have a big breakfast. In the afternoon, I go to Hoi An and play many things. In the evening, I eat a delicious meal and go to bed. I really love this summer holiday and I hope you have a good summer, too!