Como passar essas frases para voz passiva?

1 - They were mending the road, so we had to go to a different way = The road was being mended, so we had to go a different way
2 - I would have finished my homework if you hadn't annoyed me = My homework would have been finished if you hadn't annoyed me.
3 - Would it solve the problem if they came earlier? = Would the problem be solved if they came earlier?
4 - The manager postponed the meeting because of the delay = The meeting was postponed by the manager, because of the delay.
5 - They had finished the preparations by the time the guests arrived = By the time the guests arrived, the preparations had been finished.