Em đang cần lời giải gấp, giúp em với ạ

`15.` I haven't seen him since I was a student.

- S + last + V2/Ved + O + when/in/ago.. = S + haven't/hasn't + V3/Ved + O + since/for..

`16.` I last came there two years ago.

- S + last + V2/Ved + O + when/in/ago.. = S + haven't/hasn't + V3/Ved + O + since/for..

`17.` I started studying English seven years ago.

- S + have/has + V3/Ved = S + started + V-ing +..in/at/ago..

`18.` Steve has worked for this company for five years.

- S + have/has + V3/Ved = S + started + V-ing +..in/at/ago..

`19.` Have you ever driven this kind of car?

- "Bạn có kinh nghiệm nào khi lái xe kiểu này không?" = "Bạn đã từng lái xe kiểu này chưa?"

- HTHT: (?) Have/Has + S + V3/Ved..? 

- ever: đã từng

`20.` The last time Nancy came here was in 1999.

- S + haven't/hasn't + V3/Ved + O + since/for.. = The last time + S + V2/Ved + ...in/ago/..

`21.` While I was having dinner, the phone was ringing.

- While + QKTD, QKTD

- QKTD: (+) S + was/were + V-ing

`22.` When we arrived the party, David had left there.

- When + QKĐ, QKHT

- QKĐ: S + V2/Ved

- QKHT: S + had + V3/Ved