Bonjour,
il suffit de mettre l'auxiliaire "be" au temps de la phrase de départ, puis de la faire suivre par le verbe au participe passé.
1. Tickets are sold here by us
2. The steam engine was invented by someone
3. I was helped by them
4. The mail is delivered by him
5. My bike was stolen by someone
6. Breakfast is made by her
7. In Australia, english is spoken by them (ou by Australians)
8. Those people were filmed by him
La phrase 7 est grammaticalement correcte, mais ne veut pas dire grand chose au niveau du sens. Du coup il serait plus adapté de mettre "by Australians", mais le sujet de la phrase de départ est "They " et non "Australians", d'où le "them" même si cela ne signifie pas grand chose
