1. I have stepped on the brakes. Otherwise, I would have hit the child on the bicycle

→ If I hadn’t stepped on the brakes, I would have hit the child on the bicycle.

2. If you hadn't helped us, we would have been in trouble.

→ If it weren’t for your help, we would have been in trouble.

3. If it were not for your permission, he would not do that.

→ If it weren’t for your permission, he wouldn’t have done that. Is there anything else you need help with?