Riddle me now

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Across
  1. 2. An equation with 4 or more terms
  2. 5. If x/2+x/3-x/4=7, then what is x?
  3. 6. An unknown quantity or variable
  4. 7. An expression with 1 or more algebraic terms
  5. 8. Albert is 3 years older than Stephen. Six years ago, Albert's age was 4 times Stephen's age. Find Stephen's age
  6. 9. 2[x+5]=2x+10 displays this property
  7. 10. A number that is going to be raised to a power
  8. 12. If 2x+5/3=3x-10, find x
  9. 13. Index or power
Down
  1. 1. The number part of a term with variables
  2. 3. The highest power of a variable
  3. 4. The inverse of division
  4. 7. [50+44]+63=50+[44+63] displays this property
  5. 11. A linear equation contains only these polynomials