$\text{1. Her birthday used to be celebrated in the restaurant}$

$\text{2. I used to write letters to my friends when I was a student }$

$\text{3. Did she use to write in her diary before going to bed? }$

$\text{4. She used to eat a lot of sweets.}$

$\text{5. When I lived in the countryside, I used to play football}$

$\text{every weekend}$

$\text{- Cấu trúc "used to":}$

$\text{(+) S+ used to+V(inf)}$

$\text{(-) S+ didn't+use to+ V(inf)}$

$\text{(?) Did+S+use to+V(inf)}$

$\text{-Cấu trúc bị động với "used to":S+ used to+be+Vpp/ed+(by+O)}$

1)her birthday party used to celebrate in the restaurant.

2)I used to write letters to my friends when I was a student.

3)Did she use to write in her diary before going to the bed?

4)she used to eat a lot of sweets.

5)when I lived in the countryside,I used to play football every weekend.

giải thích: (+)S + used to + V nguyên mẫu

                 (-)S + didn't use to + V nguyên mẫu

                  (?)Did+ S+ use to + V nguyên mẫu?