1. The manager always welcomes new employees.

=> New employees are always welcomed by the manager

2. Janet's colleagues gave her a present when she retired.

=> Janet was given a present by her colleagues when she retired.

3. Thomas Edison invented the phonograph in 1877

=> The phonograph was invented by Thomas Edison in 1872.

4. Stephen Court has just invented an armchair that can play music.

=> An armchair that can play music has just been invented by Stephen Court.

5. Where will your company send you next year?

=> Where will you be sent by your company next year?

6. Had a special messenger delivered the package before you got to the office?

=> Had the package been delivered by a special messenger before you got to the office? 
7. The students usually hold concerts at the university.

=> The concerts are usually held at the university by the students.
8. The police found two children in the forest.

=> Two children were found in the forest by the police

9. The scientists are studying the problem carefully.

=> The problem is being carefully studied by the scientists