Divide nine into two equal parts,....

This is a riddle, and as such belongs there---but the answer is to draw a horizontal line across the number 9 making a 1 below the line and a 0 above the line. Put 1 and 0 together and you get 10.

Alternate solution--9 in Roman numerals is IX. Draw the horizontal line making IV above and I^ below. Flip the bottom over to become VI. Add IV and VI together to get X, which is 10.

Rap

sounds kind of like the Banach Tarski paradox.