Answers:
1. Let the fire brigade be summoned.
2. Let the rumor not be spread.
The rumor should not be spread.
3. Let the car be driven slowly.
4. Let the window be shut.
5. Let the work be done immediately.
6. Let the letter be posted immediately.
7. Finish the game.
8. Let the door be shut.
9. Let the book be kept on the table.
10. You are requested to give me some more time.