VI. 
1. We didn't use to go to school by bus.
2. He used to ride a bike for exercise.
3. Did Tim use to be a taxi driver?
4. He didn't use to smoke the cigarettes a day.
5. Did you use to ride a motorbike without wearing a helmet?
6. There used to be many trees on this street
VII. 
1. I didn't use to listen to Western music some years ago.
2. My mum used to be a chef in Cham restaurant, but now she is retired.
3. There used to be a market here in 2003.
4. She used to be my idol when I was a child.

VI.
1.We used to go to school by bus. 
=> We didn't use to go to school by bus.
2.Did he use to ride a bike for exercise? 
=> He used to ride a bike for exercise.
3.Tim used to be a taxi driver. 
=> Did Tim use to be a taxi driver?
4.He used to smoke ten cigarettes a day. 
=> He didn't use to smoke ten cigarettes a day.
5.You used to ride a motorbike without wearing a helmet.
=> Did you use to ride a motorbike without wearing a helmet ?

6. There didn't use to be many trees on this street.
=> There used to be many trees on this street.

VII.

1.I didn't listen to Western music some years ago.
=> I didn't use to listen to Western music some years ago.
2.My mum was a chef in Cham restaurant, but now she is retired.
=> My mum used to be a chef in Cham restaurant, but now she is retired.
3.There was a market here in 2003.
=> There used to be a market here in 2003.
4.There are more cars on the roads now.
=> There used to be fewer cars on the roads.
5.She was my idol when I was a child.
=> She used to be my idol when I was a child.