Rule 1: Passive verbs have -wa, iwa or -ewa at the end; sometimes (l) -iwa or (l)-(ewa)
Rule (2) The object of the active sentence becomes the subject of the passive sentence
e.g -My computer was stolen by a friend.-Kompiuta yangu iliimbiwa na rafiki
In Passive sentence it becomes:
A friend stole my computer or rafiki aliimba kompiuta yangu
Here are more exercises for you:
1. My sister married a Japanese
2.The rain ruined our crop
3.Their father won the race