Here are the rewritten sentences:

26. If she had known you were in the hospital, she would have visited you.
27. Unless she is very shy, she would enjoy parties.
28. If it hadn't been raining, I would have taken the children to the beach.
29. Unless the examiner had read the passage slowly, the candidates wouldn’t have understood it.
30. If people didn’t drive so fast, there wouldn’t be so many accidents.
31. If I knew his address, I would write to him.
32. If they hadn’t asked him to leave the dining room, he would have stayed because he was wearing a shirt.
33. Unless you keep silent, you'll wake the baby up.
34. If he had worked hard at school, he would have gotten a good job when he left.
35. Unless you stop talking, you won’t understand the lesson.
36. If you don't stop smoking, why are you asking?
37. If the boy weren't so young, he could go to school.