The number shown is the cube of a randomly selected 3 digit number (i.e. from 100 to 999).
Click on any one of the squares to the right of where it says "Answer:", and then you can
enter a digit of the answer (by typing it).
You can use backspace or delete to delete a digit, and you can use left and right arrow keys to
move from one digit position to another. (Note: the backspace and delete keys don't work in Opera.)
When you have entered all three digits, you will get either a congratulatory message, if you
were right, or you will get an explanation of what you did wrong.
Even after finishing, you can continue to update the digits (for example to see what happens
if you correct a wrong digit).
Or, you can press the "Try New Cube Root" button to start again with a new number.