1. Our father used to smoking when he was young -> smoke
2. They are interested in do something different at weekend -> doing
3. The store owners have been concerned about the mall since a few months -> for
4. She enjoys to play badminton with her friends after school -> playing
5. He likes gardening but he dislikes to do the housework -> doing
6. Ba always gets excellent grades because he study hardly -> hard 
7. Minh didn't meet his younger brother for five years -> hasn't met
8. There are many differently ways of learing words -> different
9. He lived in this city since 2007 -> has lived 
10. Her bag is different to mine -> from
11. The meeting will be held in April 2nd -> on
12. She speaks English quite good -> well
13. They didn't reported a book last week -> report
14. I have not see him for last Sunday -> I didn't see him last Sunday
15. She has went to the mountain -> mountains