integers crossword

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Across
  1. 3. number sum of whole numbers is again a which number
  2. 6. five times two is
  3. 7. which is an additive identity for whole numbers
Down
  1. 1. -3 x -4
  2. 2. multiplication of two negative integers is which integer?
  3. 4. 4+4
  4. 5. we multiply positive integer and negative integer and add which sign?