`1.` They used to go to school by bike when they were young.

`-` used + to V-inf : đã từng làm gì trong quá khứ

`2.` Ann used to be a secretary for many years, but now she owns her own business.

`-` used + to be : đã từng là gì trong quá khứ

`3.` We used to have fresh eggs every morning when we raised our own chickens

`-` used + to V-inf : đã từng làm gì trong quá khứ

`4.` The town used to be some old buildings when I was young.

`-` used + to be : đã từng là gì trong quá khứ

`-` `\text{S + used to + V-inf :}` Đã từng

`-` `\text{S + used to be + sth / sb :}` Đã từng là ...

`17`.They used to go to school by bike when they were young

`18`.Ann used to be a secretary for many years , but now she owns her own business

`19`.We used to have fresh eggs every morning when we raised our own chickens

`20`.The town used to have some old buildings when I was young

`\text{# TF}`