Active: Subject+verb present+comp(DO/IO)
Passive: DO/IO+am/are/is+past participle+by+subj
Active: They are repairing the streets this month
Passive: DO/I+am/are/is+being+past participle+by+subj- The streets are being repaired this month by them
Active: They built that skyscraper in 1934.
Passive: DO/IO+was/were+past participle+by+subj- That skyscraper was built in 1934 by them
Active: The salesman was helping the customer when the thief came into the store
Passive: DO/IO+was/were+being+past participle- The customer was being helped by the salesman when the thief came into the store