`1,` I last met my best friend when I was 18 years old

`@` S1 +  last + V2/ed + when + S2 + V2/ed ..

`->` S1 + have/has + V3/ed + since + S2 + V2/ed ...

`2,` The last time my children took to the supermarket was in grade 5

`@` The last time + S2 + V2/ed + ... + was + thời gian trong quá khứ

`->` S + haven't/hasn't + V3/ed + ...+ for/since + thời gian

`3,` They have studied for 5 years 

`@` S + started/began + V-ing/ to V + thời gian trong quá khứ

`->` S + have/has + V3/ed + for/since + thời gian

`4,` I haven't seen my father for 10 years ago

`@` The last time + S + V2/ed + ... + was + thời gian trong quá khứ

`->` S + haven't/hasn't + V3/ed + ...+ for/since + thời gian

1. I haven't met my best friend since I was 18 years old.

->I last met my friend when I was 18 years old.

+) S+haven't/hasn't+V-pll+since/for..

=S+last +V2/V-ed+...

2. My children haven't been taken to the supermarket since they were in grade 5.

->The last time my children took to the supermarket when they were in grade 5

+)

S+haven't/hasn't+V-pll+since/for..

 = the last time + S+V2/V-ed+was+tgian(+ago)

3. They started studying Spanish and Chinese 5 years ago.

->They have studied spainish and chinese for 5 years

4.The last time I saw my father was 10 years ago.

->I have not seen my father for 10 years