` 5`. Dennis used to smoke three years ago.

` 6`. My parents used to live in the USA when they were young.

` 7`. Jim used to be my best friend.

` 8`. My uncle used to be a nationnal swimming champion.

` 9`. I didn't used to like eating ice-cream.

` 10`. Barbara used to stay with an Italian family when she was Italy.

` -----`

` @` Used to

` (+)` S + used to + V-inf + ...

` (-)` S + didn't used to + V-inf + ...

` (?)` Did + S + used to + V-inf + ...?

` -` Đã từng làm gì mà giờ không còn

5 . Dennis used to smoke three years ago .

6 . My parents used to live in the USA when they were young .

7 . Jim used to be my beat friend , but we aren't friends anymore .

8 . My uncle used to be a national swimming champion .

9 . I didn't use to eat ice cream when i was a child .

10 . Barbara used to stay with an Italian family when she was Italy .

- Cấu trúc used to : 

+) S + used to + Vo + O ...

-)  S + didn't use to + Vo + O ...

?) Did S use to + Vo + O ... ? 

                     #goodluck