Cấu trúc used to:

S + used to + V:  trước đây thường làm gì nhưng giờ không làm nữa

S + didn't use to + V: trước đây thường không làm gì nhưng bây giờ lại làm

5. Children didn't use to play with high-tech devices at an early age.

6. The students didn't use to go to school by public transportation.

7. My city used to be a tourist destination.

8. Traffic jams didn't use to happen when I was small.

$\text{5.}$ Children didn't use to play with high-tech devices at an early age .

$\text{6.}$ The students didn't use to go to school by public transportation .

$\text{7.}$ My city used to be a tourist destination.

$\text{8.}$ Traffic jams didn't use to happen when I was small.

→ used to + V-inf : đã từng làm j 

→ didn't use + V-inf 

→ Did + S + use + V-inf + O ? 

$#Lynkk$