1. Thanks a lot for your letter. I was happy to hear from you again.
  2. Thank you for your letter. I haven’t heard from you for ages.
  3. I’m sorry I haven’t answered earlier but I was really busy with my school.
  4. Sorry, I’d better go now as I have to do my homework.
  5. Sorry, I’ve got to go now. It’s time for...
  6. Sorry for not writing you so long.
  7. Unfortunately, I must go now as I have to do a project.
  8. I’m sorry I haven’t written for so long but I’ve been really busy with...
  9. Sorry, I didn’t write for a long time because I had some problems at school.
  10. Sorry, I haven’t written for a long time because I have had some problems.
  11. Sorry, I didn’t answer earlier but I was very busy.
Language (The language you are writing in)
English