Mina's Algebraic Terms Crossward Puzzle

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Across
  1. 5. If you add or multiply three or more numbers, the order doesn't matter
  2. 9. The center of the coordinates plane
  3. 11. The pieces you separate in an equation
  4. 12. Inverse: The sum of two numbers is zero
  5. 13. If you add or multiply two numbers, the order doesn't matter
  6. 15. A number by itself
  7. 16. The answer to an addition problem
  8. 17. Addition _______ of equality
  9. 18. The amount of surface, labeled in units squared
Down
  1. 1. The number in front of the variable
  2. 2. Inverse: The product of two numbers being one
  3. 3. An (x,y) point on a grid
  4. 4. Multiplication property of _____
  5. 6. The four regions of the coordinate plane
  6. 7. A repeating or ending decimal (fraction)
  7. 8. The distance around a figure, labeled in units
  8. 10. The answer to a multiplication problem
  9. 14. A non-repeating and non-ending decimal