16) She hasn’t had a swim for five years

=>She last had a swim five years ago

17) They last talked to each other two months ago

=>They haven't talked to each other for two months

18) The last time she saw her elder sister was in 1999

=>She hasn't seen her elder sister since 1999

19) She hasn’t written to me for years

=>It's years since she last wrote to me.

20) Robert and Catherine have been married for ten years

==> It's ten years since Robert and Catherine married