Ответ:

  1. Linda, you have written four books. How long have you been writing books?
  2. I have been writing books since I was eleven. But I haven’t written four books. I have just written another one, so that’s five altogether.
  3. How long have you been living in England?
  4. I haven’t lived in England long. I have been staying with my cousin since I arrived two weeks ago.
  5. How long have you been learning English?
  6. I have been learning English for ten years.

Present perfect употребляется для завершённых результатов, а Present perfect continuous — для длительных действий, продолжающихся до настоящего момента.