`10.` 

`-` They last ate this kind of seafood years ago.

`-` The last time they ate this kind of seafood was years ago.

`-` It's years since they last ate this kind of seafood.

`->` S + last + Ved/V2 + time + ago

`=` S + have/has not + P2 + for + time

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

`=` It's + time + since + S + last + Ved/V2

`11.`

`-` Olivier last saw his aunt years ago.

`-` The last time Olivier saw his aunt was years ago.

`-` It's years since Olivier last saw his aunt.

`12.` My mother has taught in this school for `15` years.

`->` S + began + V-ing + time + ago

`=` S + have/has + P2 + for + time