Prep Puzzle

12345678910
Across
  1. 3. How do we call numbers: 2, 3, 5, 7...
  2. 4. Determine if x-13 is even or odd when x is even.
  3. 5. What is the smallest natural number?
  4. 9. In the operation 3.8=24, 3 is called ...
  5. 10. How many positive integers 12 have?
Down
  1. 1. In the operation 12+13=25, 13 is called ...
  2. 2. Which one is 3rd?
  3. 3. In the operation 3.8=24, 24 is called ...
  4. 6. How do we call numbers 0, 2, 4, 6 ...
  5. 7. In the operation 12+13=25, 25 is called ...
  6. 8. 3...4=7 What is the missing operation?