3. Hurry up, or we will be late for the exam.
- If we don't hurry, we'll be late
4. They don't understand you because you don't talk to them often.
- If you don't talk often, they won't understand you.
5. The apartments are not clearly numbered so it is difficult to find anyone.
=> If the apartment is not numbered, it is very difficult to find.
6.He doesn't see the signal so he doesn't stop his car
If he saw the signal,he'd stop his car