+ and - integers

123456
Across
  1. 1. 999+1=1000
  2. 4. 11x55=605
  3. 5. 400--50=450
  4. 6. 6x9=54
Down
  1. 1. 38x4=152
  2. 2. 9x4=36
  3. 3. 50--50=100