Used to

Structure: Used to (affirmative)

When using the expression used to ?

structure: used to (interrogative)

example (negative sentence)

structure: used to (negative)

example (interrogative sentence)

Did+ subect + use to + V(infinitive)+ Complement?

We use this expression to indicate something that occurred or happened in the past in a habitual way and nowadays it no longer happens.

Food didn’t use to be so expensive.

Subject.+ used to + V(infinitive)+ Complement.

Did you use to eat sushi in Japan? Yes, I used to / No I didn't use to

Subject.+ didn't + use to + V(infinitive)+ Complement.