More kids riddles.

- Once, because after you subtract it's not 25 anymore.
- 1 and 9.
- 2 and 2.
- 1, 2 and 3. 1 x 2 x 3 = 1 + 2 + 3 = 6
- Any number and 1.
- 25 = 5² and 36 = 6².
- 36 = 2 x 3 x 6.
- The number 8. It's made up of two zeros, one on top of the other.
- (9⁹)⁹ = 9³⁸⁷⁴²⁰⁴⁸⁹, which is a number with more than 369 million digits.