Ответ:
1) If you had broken your leg you would have played in the match.
2) If you had pressed this button, the computer would have turned on.
3) If you had heated water, it would have boiled.
4) If we had played better we would have won the game.
5) Derek had missed the flight if he would have come to the airport earlier.
6) If the burglars had tried break in, the alarm system would have gone off.
7) If Samanta had helped me in the kitchen I would have prepared dinner.
8) Sam had done everything in time if the teachers wouldn`t given so much homework.
Вроде все так