$1.$ The last time we went to the concert was one year ago.

- S + haven't/ hasn't + V (-ed/Pii) + for + time = S + last + V (-ed/V2) + time + ago.

$2.$ We haven't seen our grandfather for two years. 

- S + last + V (-ed/V2) + time + ago = S + haven't/ hasn't + V (-ed/Pii) + for + time.

$3.$ This is the first time I have read such a romantic story.

- S + have/ has + never + V (-ed/ Pii) + before = This is the first time + S + have/ has + V (-ed/ Pii) + O.

$4.$ My father hasn't seen my uncle for nearly 20 years.

- It's + time + since + S + V (-ed/ Pii) + O = S + haven't/ hasn't + V (-ed/Pii) + for + time.

$5.$ It's over 20 years since he been back to his village.

- S + haven't/ hasn't + V (-ed/Pii) + for + time = It's + time + since + S + V (-ed/ Pii) + O.

$6.$ Đề có sai không ạ? Trong đề không có chủ ngữ hay từ nào liên quan đến "We" nhưng khi chuyển đổi thì lại có ạ?

$7.$ We haven't gone to the cinema for 2 years.

- S + last + V (-ed/V2) + time + ago = S + haven't/ hasn't + V (-ed/Pii) + for + time.

$8.$ We haven't seen him since Monday.

- S + last + V (-ed/V2) + time + ago = S + haven't/ hasn't + V (-ed/Pii) + since + time.

$9.$ I haven't seen David since 1989.

- S + last + V (-ed/V2) + time + ago = S + haven't/ hasn't + V (-ed/Pii) + since + time.