Предложения надо "перевести" в пассивный залог. 1.he broke my watch. 2.the teacher explained the rule to the students. 3.the often asks me to help them. 4.they usually do written exercises in class. 5.she will make a new discovery soon. 6.steve will make a report alt the conference.

1. My watch was broken by him.
2. The rule was explained to the students by the teacher.
3. I am often asked for help. 
4. Written exercises are usually done by them in class.
5. A new discovery will be made by her soon.
6. A report will be made by Steve at the conference.