Math

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Across
  1. 2. 10000-8400
  2. 3. 600+70
  3. 4. 9+1
  4. 5. a+20=61
  5. 7. a-1=219
Down
  1. 1. 60+70
  2. 2. 100x10
  3. 3. a-200=-131
  4. 4. 12x12
  5. 6. a(2x2)=400