6.it is the first time I have met such a famous singer
7.it is the first time I have been to the ballet
8.we last saw Tom when he moved to Bristol
9. The last time I wore that dress was at Barbara's wedding
+last time + S + Verb(ed/PI) +…+ was + khoảng thời gian + ago
= S + Last + Verb(ed/PI) + khoảng thời gian + ago
= S + have/ has + not + Verb(PII)+…+ for + khoảng thời gian
= It + is + khoảng thời gian + since + S + Verb
+This is the first time + S + have/has + P2: Lần đầu làm gì
=S +have/has + never + P2 + before
= S+ have/has not + P2 + before