When the mini-game is about to begin, quickly remember the numbers, then close your Nintendo DS screen. Your Nintendo DS will be in Sleep mode. Write down the numbers you remember, and solve the mathemagic. Once you know the answer, open up your Nintendo DS, and prepare to copy the answer as fast as possible. Keep doing this until you get the max score (9,999) and Whyt's Summoner/Black Mage costume at the end.
