Linear Equation Puzzle

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Across
  1. 4. A letter that stands for a number you don’t know yet
  2. 6. The value that makes an equation true
  3. 7. Replacing a variable with a number
  4. 10. The point where a line crosses the horizontal axis
  5. 11. A rule that assigns exactly one output to each input
  6. 13. Describes an equation that graphs as a straight line
  7. 15. A pair of numbers showing a position on a graph
  8. 16. A property used to multiply across parentheses
  9. 18. To make an expression easier to work with
  10. 19. A reference line on a graph
Down
  1. 1. Tells how steep a line is
  2. 2. A math phrase without an equals sign
  3. 3. A math sentence showing two sides are equal
  4. 5. A number that does not change
  5. 8. A single part of an expression or equation
  6. 9. The point where a line crosses the vertical axis
  7. 12. The point (0, 0) on a graph
  8. 14. A visual way to show an equation or data
  9. 15. A number that multiplies a variable
  10. 17. Where a line crosses an axis