В треугольнике АВС АС=12см, ВС=9см. Какой может быть сторона АВ:а) 21см; б) 3см; в)17см; 23см?

Put the verbs in brackets into the correct tense, then identify the types
of conditionals:
1. If you ……… (not/put up) this shelf, you won’t have anywhere to
put your books.
2. If he ……… (change) jobs, he would be a lot happier.
3. If I were you, I ……… (tell) her how you feel.
4. If you continue to shout so loudly, you ……… (wake up) the baby.
5. Even if he ……… (ask) them, they wouldn't have agreed to come.
6. Unless you … (feel) any better, you can take the rest of the day off.
7. If she ……… (not/ threaten) him, he wouldn't have left.
8. I ……… (not/trust) him if I were you.
9. If you’re patient for a few minutes, I ……… (be able) to finish this.
10. He ……… (not/go) with her if he had known she would behave so
irresponsibly.
11. I wouldn’t have been able to do it unless she ……… (help) me.
12. Sometimes if you ……… (take) a chance, it pays off.
13. If he …… (wake up) earlier, he wouldn’t have been late for work.
14. If they will go on making so much noise, I … (have to) punish them.
15. If we ……… (intend) to spend the day in London, we would have
bought a day pass.
16. Keep your voice down in case he ……… (overhear) us.
17. If she ……… (be) more experienced, she would be more likely to
get a job.
18. If the food ……… (not/be) so bad, we wouldn’t have complained.
19. Sales will increase provided that the advertising campaign ………
(be) successful.
20. If you ……… (spend) less on clothes, you would be able to save
some money.
21. If I ……… (be) you, I wouldn’t drive in the snow.
22. Peter ……… (be able to) help you if he was here.
23. If I had closed the window, the cat ……… (not/jump) out

Плииииз хэлп((( я не пойм что тут вставлять нужно

1You study a lot of subjects, don't you ?
2You can play a musical instrument, can't you?
3You don't speak French, do you?
4You began to study English 4 years ago, didn't you?
5Your teachers aren't British, are they?
6You weren't in London this summer, were you?
7All your friends would like to visit Britain, wouldn't you?

 Перевод,и объяснение почему вставлено don't  и все остальные.
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