1. He didn't hurry, so he missed the train.
⇒If he had hurried ,he couldn't miss the train
2. My brother didn't leave the car keys, so I couldn't pick him up to the station.
⇒If my brother had left the car keys ,i could pick him him up to the station.
3. We didn't go because it rained
⇒If it hadn't rained we would have gone
4. He lost his job because he was late every day
⇒If he hadn't been late everyday he wouldn't have lost his job.