1) He has not written to me since April. => The last time 2) She hasn't had a swim for five years => She last 3) They last talked to each other two months ago => They haven't. 4) The last time she saw her elder sister was in 1999 =>She hasn't 5) She hasn't written to me for years => It's years........ 6) Robert and Catherine have been married for ten years. => It's ten years

1. The last time he wrote to me was in April

-> The last time + S + V2/ed + was in time

= S + have/has + not + V3/ed + since time

2. She last had a swim five years ago

-> S + last + V2/ed + time ago

3. They haven't talked to each other for two months

-> S + have/has + not + V3/ed + for time

4. She hasn't seen her elder sister since 1999

-> The last time + S + V2/ed + was in time

= S + have/has + not + V3/ed + since time

5. It's years since she last wrote to me

-> S + have/has + not + V3/ed + for time

= S + time + since + S + last + V2/ed

6. It's ten years since Robert and Catherine were married

-> It's + time + since + S + (last) + V2/ed