Viết lại câu với Used to hoặc didn't

`1`.We used to light our houses with candles.

`2`.Sailors used to be guided by strars.

`3`.People used to cook on wood fires.

`4`.It used to take me several days to go to London.

`5`.Books used to be written by hand.

`6`.People used to travel on foot.

`7`.They used to make their own bread.

`8`.The old sailro used to drink lots of whisky.

`9`.Mr. Smith used to smoke cigars.

`10`.Bill used to work very hard.

`11`.I used to have a lot of money but I lost it all when my business failed.

`12` I quite like classical music now, although I didn't used to keen on it when I was younger.

`13`.I used to be interested in my work.

`@`Công thức

`+`S + used to + V-inf + O : đã từng làm gì

`-`S + didn't + use to + V-inf + O : chưa từng làm gì

`?` Did + S + use to + V-inf + O ? : chưa từng làm gì?