`1.` `(+)` They used to go beach every summer.

      `(-)` They didn't use to go beach every summer.

      `(?)` Did they use to go beach every summer?

`2.` `(+)` I used to walk school.

      `(-)` I didn't use to walk school.

      `(?)` Did you use to walk school?

`3.` `(+)` They used to have short hair when they studied at university.

      `(-)` They didn't use to have short hair when they studied at university.

      `(?)` Did they use to have short hair when they studied at university?

`4.` `(+)` There used to be post office here.

      `(-)` There didn't use to be post office here.

      `(?)` Did there use to be post office here?

_______________________________________________

`+` Cấu trúc:
`(+)` Khẳng định: S + used + to + V_inf

`(-)` Phủ định: S + didn't + use to + V_inf

`(?)` Nghi Vấn: Did + S + use to + V_inf...?

`-` Nghĩa* Đã từng làm điều gì đó trong quá khứ và ko còn xảy ra ở hiện tại

`@Ame`

`#howardamelia`

`-----------`

`1` 

`+` They used to go to the beach every summer.

`-` They didn't use to go to the beach every summer.

`?` Did they use to go to the beach every summer?

``

`2` 

`+` I used to walk to school.

`-` I didn't use to walk to school.

`?` Did I use to walk to school?

``

`3` 

`+` There used to be a post office here.

`-` There didn't use to be a post office here.

`?` Did there use to be a post office here?

`--------`

`(+)` S `+` used `+` to V

`(-)` S `+` did not `+` use `+` to V

`(?)` Did `+` S `+` use `+` to V `?`