11. We started learning English five years ago.
=> We have been learning English for five years.

12. I began living in Ho Chi Minh City when I was 8.
=> I have been living in Ho Chi Minh City since I was 8.

13. She has taught the children in this remote village for five months.
=> She started teaching the children in this remote village five months ago.

14. He has written to me since April.
=> The last time he wrote to me was in April.

15. She hasn't had a swim for five years.
=> She last had a swim five years ago.

16. They last talked to each other two months ago.
=> They haven't talked to each other for two months.

17. The last time she saw her elder sister was in 1999.
=> She hasn't seen her elder sister since 1999.

18. She hasn't written to me for years.
=> It's years since she wrote to me.

19. Robert and Catherine have been married for ten years.
=> It's ten years since Robert and Catherine got married.

20. We have not jogged since August.
=> The last time we jogged was in August.