1. The company employs three hundred people. -> Three hundred people are employed by the company. (Present Simple)
2. B & K have built a new cinema complex near the airport. -> A new cinema complex near the airport has been built by B & K. (Present Perfect)
3. John wrote the essay. -> The essay was written by John. (Past Simple)
4. The Mayor will open the new theatre this Sunday. -> The new theatre will be opened by the Mayor this Sunday. (Future Simple)