18.2
2. used
3. used to be
4. did
5. used to
6. use
7. to
8. be able
9. didn’t
18.3
2. She used to be very lazy but she works hard these days.
3. She didn’t use to like cheese but she eats lots of cheese now.
4. She used to play the piano but she hasn’t played the piano for a long time.
5. She never used to drink a tea but she likes it now very much.
6. She used to have a dog but her dog died two years ago.
18.4
3. I used to eat lots of sweets but now I eat more vegetables.
4. I used to play cards but now I only play chess.
5. I used to be very lazy but now I like to learn hard.
6. I didn’t use to travel by plane but now I fly a lot.
7. I didn’t use to have a pet but now I have two small dogs.
8. I didn’t use to do sports but now I do sports three times a week.
Объяснение:
John won't become an engineer.
Susan won't miss her train.
Nancy won't help him with this project.
It won't snow the day after tomorrow.
He won't pass the test.
I won't call you tonight.
Объяснение об образовании отрицательного предложения в Future Simple:I, you, we, they, he, she, it + will not (won't) + 
Для построения отриц. предл. в Future Simple используется вс глагол will not (или сокращение - won't). В предложениях я использовал won't, т.к. данный вариант был указан в примере. Вы же можете абсолютно везде использовать полную форму will not.
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