it's pretty easy.

123456789101112
Across
  1. 3. 4+
  2. 6. One number in the equation
  3. 8. 1
  4. 9. Degree of 4
  5. 12. First number in Standard form
Down
  1. 1. Ax+By=C
  2. 2. the very tiny number
  3. 4. 2
  4. 5. 3
  5. 7. Degree of 3
  6. 9. Degree of 2
  7. 10. a line
  8. 11. The biggest tiny number