6. He wanted to know if Debbie had been working there long
-> S wanted to know if S V(lt)
7. She wondered why Maria was crying
-> S wondered wh- S V(lt)
8. We wanted to know what kind of holiday Marco had had
-> S wanted to know wh- S V(lt)
9. She wondered if I had studied hard for the exam
-> -> S wondered if S V(lt)
10. They ask us how long we have been living there
-> ask chia ở thì hiện tại nên vế sau không lùi thì
11. She asked us if Ted and Alice would be at the party

-> S asked sb if S V(lt)
12. She asked me what I had thought of the performance the day before

-> S asked sb wh- S V(lt)
13. He asked me who I had been looking for

-> S asked sb wh- S V(lt)
14. He asked me whether meals were included in the price

-> S asked sb whether S V(lt)
15. I wanted to know how I could solve the problem 

-> S wondered wh- S V(lt)