1. If she did her hair differently, she would look quite nice.

- Unless she did her hair differently, she wouldn't look quite nice.

2. Unless you keep silent, you won't understand the lesson.

- If you don't keep silent, you won't understand the lesson.

3. If John had played for our football team, we would not have lost the game.

- Unless John had played for our football team, we wouldn't not have lost the game.

B. If clauses (type 2)

4. I don't know the answer, so I can't tell you.

- If I knew the answer, I could tell you.

5. Peter is fat because he eats so many chips.

- If Peter didn't eat so many chips, he wouldn't be fat.

6. Tony doesn't understand the math problem, so he can't solve it.

- If Tom understood  the math problem, he could solve it.

7. He doesn't help her because he doesn't know her problem.

- If he knew her problem, he would help her.

C. If clauses (type 3)

8. His parents were very disappointed because he failed his exam.

- If he hadn't failed his exam, his parents wouldn't have been very disappointed.

9. He didn't pass the final exam because he didn't work hard enough.

- If he had worked hard enough, he would have passed the final exam.

10. He didn't hurry, so he missed the train.

- If he had hurried, he wouldn't have missed the train.