1. Go right now or you will be late for the train.
→ If you go left now you will be late for the train.
2. As she is often absent from class, she can’t keep pace with her classmates.
→ If she doesn't often absent from class ,she will keep pace with her classmate.
3. I couldn’t write to Alice because I didn’t know her address.
→ If I know her dress, I could write to Alice.