1. The last time she went out with him was 5 months ago. 

(Chú ý không nhầm vs thì HTHT)

2. This is the first time we have seen such a cruel mother.

3. We haven't seen Mr. Jones for 2 years.

(Since đi vs mốc TG vd since 2023, for đi vs khoảng TG vd for 2 days)

4. I haven't visited the USA before. ( Câu 2 và câu 4 là đối nhau)

`1.` The last time she went out with him was 5 months ago.

`->` S + have/has + not + Vpp + for/since + time

`=` The last time + S + V2/ed + was + time + ago

`2.` This is the first time we have ever seen such a cruel mother.

`->` This is the first time + S + have/has + V3/-ed + such a/an+ adj + N

`=` S + have/has + never + V3/ed + such a/an+ adj + N

`3.` We haven't seen Mr.Jones for two years.

`->` S + have/has + not + Vpp + for/since + time

`=` It is + time + since + S (last) + V2/ed

`4.` I haven't visited the USA before.

`->` This is the first time + S + have/has + V3/-ed

`=` S + have/has + never (not) + V3/-ed + before