12. All passengers have to fasten their seatbelts. (must)
$\to$ All passengers must fasten their seatbelts.
13. You don't need to bring a present when you visit your friend's house in my country. (have to)
$\to$ You haven't to bring a present when you visit your friend's house in my country.
14. It's a good idea to add coconut to cook the best five-colored sticky rice. (should)
$\to$ It's should add coconut to cook the best five-colored sticky rice.
15. '' You'd better not lend him any more money, Elizabeth'' said John. (advised)
$\to$ John advised Elizabeth should not lend him more money.
16. My suit needs to be cleaned before the interview. (must)
$\to$ My suit must be cleaned before the interview.
17. You don't have to wear ties if you don't like them. (It's not)
$\to$ It's not important to wear ties if you don't like them.
18. If I were you, I would not eat that cake. (should)
$\to$ You shouldn't eat that cake.