Ответ:

1) He will buy the tickets tomorrow. - The tickets will be bought by him tomorrow.

2) She found this book in the library. - This book was found by her in the library.

3) You check the bill every month. - The bill is checked by you every month.

4) We gave grants to our best students yesterday. - Our best students were given grants by us.

5) The pupils laughed at the freshman in their class. - The freshman was laughed in the class by the pupils.

6) They usually discuss the shows. - The shows are usually discussed by them.

Объяснение:

Субъект действия, выраженный местоимением в данных предложениях, можно не использовать в предложении, на нем нет особой смысловой нагрузки. Например: The tickets will be bought  tomorrow. - Билеты будут куплены завтра.

1. The tickets will be bought tomorrow.
2. This book was found by her in the library.
3. The bill is checked every month.
4. Our best students were given grants yesterday.
5. The freshman in their class was laughed at by the pupils.
6. The shows are usually discussed.