Math crossword

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Across
  1. 6. What you need when you don't have wifi
  2. 7. Regular deposit that adds up
  3. 8. A thing you do when you want to spend less
  4. 10. Another word for surgery
  5. 12. Payments for buying a house
  6. 14. How big is "y"?
  7. 15. Not a 2D shape
  8. 17. An equation in pictures (bar ___)
  9. 19. sine/cosine = tangent
  10. 20. Expression with many terms
Down
  1. 1. Expression with an "=" sign
  2. 2. 1/2
  3. 3. Opposite of nice
  4. 4. I work at _______ Canada
  5. 5. Straight line
  6. 9. The study of shapes
  7. 11. x^2
  8. 13. Shape with 3 sides
  9. 16. It changes
  10. 18. Opposite of known