1. We used to live in a flat when I was a child.

2. People didn't use to have mobile phone 20 years ago.

3. Did Jim use to go swimming every weekend?

4. My father used to smoke but he gave up 5 years ago.

5. Lily didn't use to cook much, but now she makes dinner every day.

6. Không chắc chắn về trường hợp này. Vì use là động từ

7. People didn't use to buy so much stuff as they do today.

$\text{1}$ We used to live in a flat when I was a child.

$\text{2}$ People didn't use to have mobile phone 20 years ago.

$\text{3}$ Did Jim use to go swimming every weekend?

$\text{4}$ My father used to smoke but he gave up 5 years ago.

$\text{5}$ Lily didn't use to cook much, but now she makes dinner every day.

$\text{6}$ Did there use to be a supermarket ơn the corner ?

$\text{7}$ People didn't use to buy so much stuff as they do today.

→ S + used to + V-inf + O 

→ S + didn't + use to + V-inf + O 

→ Did + S + use to + V-inf + O ? 

$\text{@Zyy}$