1. I have to work tomorrow evening, so I can’t meet you.
If I didn't have to work tomorrow evening, i could meet you.
2. There is a chance we won’t pass the test.
We might not pass the test
3. We don’t visit you very often because you live so far away.
If you  didn't live so far away , we could  visit you very often
4. There isn’t anywhere else in the world as beautiful as this place.
This is the most beautiful place  in the world
5. Perhaps, the products of the future will be better than today’s.
The products of the future might  be better than today’s.