decimal subtraction and addition by hamish

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Across
  1. 4. 51187.581-17036.748
  2. 5. 242.6912+416.1472
  3. 9. 64483.625-26962.782
  4. 10. 3832.1735-2109.3624
  5. 11. 9787.9683-5886.6931
Down
  1. 1. 5731.791+7848.537
  2. 2. 27432.696+15123.614
  3. 3. 4.25+5.76
  4. 6. 31.13+6.09
  5. 7. 105.278365+19.643912
  6. 8. 430.564+5800.538