Numbers, colours and other things

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Across
  1. 4. 1
  2. 6. colour
  3. 8. ...expensive book
  4. 11. 17
  5. 12. 13
  6. 13. colour
  7. 14. 5
  8. 15. colour
  9. 16. plural: box
  10. 17. Please, raise your... .
  11. 18. colour
Down
  1. 1. plural: man
  2. 2. colour
  3. 3. Let's compare the... .
  4. 5. 8
  5. 7. 20
  6. 9. 9
  7. 10. plural: child
  8. 11. plural: sandwich
  9. 16. colour