`1.` We used to go to school on foot.

`-` Cấu trúc: used to + V

`2.` It's about 30km from my town to Ha Long Bay.

`-` Cấu trúc: It's (about) + khoảng cách + from ... to ...

`3.` My family used to go on holiday seaside in the summer.

`-` Cấu trúc: used to + V

`4.` How long does it take you from Ha Noi to Sapa?

`-` Cấu trúc: How long does it take + sb + from ... to ...?

`5.` There used to be a factory in the town center but it was moved to the suburbs.

`-` Cấu trúc: used to + V

`6.` You must learn about road safety before riding your bike on the road.

`-` Cấu trúc: must + V