Maths Crossword - Solve the "?"

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Across
  1. 4. 55 - 12 = ? + 21
  2. 5. 50 - ? = 42 + 8
  3. 10. 36 + 25 = ? - 27
  4. 11. 42 - 12 = ? + ?
  5. 13. 156 - ? = 48 + 12
  6. 15. ? - 36 = 10 + 3
  7. 16. 28 + 25 = 52 + ?
  8. 17. ? + ? = 100 - 20
  9. 18. 20 + 14 = 45 - ?
Down
  1. 1. ? + 4 = 30 - 10
  2. 2. x + 81 = 118 - 17
  3. 3. 4 x ? = 32 ÷ 2
  4. 4. 11 + 25 = ? + 3
  5. 6. 100 + 25 = 43 + ?
  6. 7. 55 + 32 = x + 31
  7. 8. 25 + ? = 91 + 11
  8. 9. 25 - ? = 10 + 5
  9. 11. 70 - 28 = 92 - ?
  10. 12. 250 - 225 = x - 66
  11. 14. 58 + ? = 84 - 17