1. Thanks to his aunt’s legacy of $ 10.000 he was able to buy the house he wanted.

=> Had his aunt not left him a legacy of $ 10.000.he couldn't have bought the house he wanted.

2. If I had known she was sick, I would have visited her.

=>Had I known she was sick, I would have visited her.

3. If the train should be delayed, I shall send the telegram.

=>Should the train to be delayed,I shall send the telegram.

4. Supposing it were true, how would we laugh?

=>Were it to be true,, how would we laugh?

5. The only reason the party was a success was that a famous film star attended.

=> Had it not been for the attendance of a famous film star,the party wouldn't have been successful.

6. The only thing that prevented the passing of the bill was the death of the Prime Minister.

=> Had it not been for the death of the Prime Misnister,the passing of the bill wouldn't have been prevented.

7. If I met the author one day, I would ask him to sign my copy of his new book.

=> Were I to meet the author one day, I would ask him to sign my copy of his new book.

8. I didn’t realized he was the author and that’s why I was so rude about his book.

=> Had I realized he was the author,I wouldn't have been so rude about his book.

9. Please let me know if you wish to keep the books any longer.

=> Should you let me know if you wish to keep the books any longer.

10. If I were the Prime Minister, I would reduce taxes.

=>Were I to be the Prime Minister, I would reduce taxes.

11. I can meet you if you arrive before eleven.

=>So long as you arrive before eleven,I can meet you.

12. Your car may break down on the rough mountain road, so take plenty of spare parts.

=> In case your car may break down on the rough mountain road, take plenty of spare parts.

13. Without this treatment, the patient would have died

=> If he hadn't treated,the patient would have died

14. You should take a map because you might get lost in those mountains.

=> In case you might get lost in those mountains,You should take a map

15. Without his help we would all have died.

=> If it hadn't been for his help,we would all have died.