1.we couldn't go out because the weather was so bad
=> if
2.Mary was not injured in the crash because she was wearing a seat belt
=> if
3.you didn't eat breakfast so you are hungry now
=>if
4.i can't retell the film now because i didn't watch it last night
=> if
5.i bought the car yesterday so i run out of money now
=>if
6.he didn't go to the class regularly so he can't take part in the competition now
=>if
7.he doesn't have enough money, so he doesn't buy a house
=>if
1.we couldn't go out because the weather was so bad
=> if the weather hadn't been so bad, we could have gone out
2.Mary was not injured in the crash because she was wearing a seat belt
=> if Mary hadn't been wearing a seat belt, she would have been injured in the crash
3.you didn't eat breakfast so you are hungry now
=>if you had eaten breakfast, you wouldn't be hungry now
4.i can't retell the film now because i didn't watch it last night
=> if I had watched the film last night, I could retell it now
5.i bought the car yesterday so i run out of money now
=>if I hadn't bought the car yesterday, I wouldn't run out of money now
6.he didn't go to the class regularly so he can't take part in the competition now
=>if he had gone to the class regularly, he could take part in the competition now
7.he doesn't have enough money, so he doesn't buy a house
=>if he had enough money, he would buy a new house