Solving Equations Crossword Puzzle

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Across
  1. 2. the number that is with a variable
  2. 4. whole numbers and their opposite
  3. 5. the mnemonic device used to help us solve for the value of an unknown variable
  4. 7. a letter used to represent a number
  5. 8. having the same value
  6. 9. the mneumonic device used when solving for numerical expressions
Down
  1. 1. to find the answer
  2. 3. a number that is known by itself
  3. 4. to separate from others
  4. 6. addition, subtraction, multiplication, and division