Cruzadinha usando as 4 operações:

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Across
  1. 3. 8x9+8
  2. 4. 72:6
  3. 8. 5x5+5
  4. 10. 8x8+6
  5. 13. 210:5
  6. 14. 4x4+1
  7. 15. 7x8+5
Down
  1. 1. 6x6-22
  2. 2. 9x9-21
  3. 5. 7x7-9
  4. 6. 5x10-30
  5. 7. 276:6
  6. 9. 9x6-13
  7. 11. 3x5+1
  8. 12. 6x7+8