Select one number from 10 to 99, use the number on the single digit plus the number on tens digit, and then use the number you select minus the sum. For example: if you pick up number 23, 2+3=5, use 23-5=18. Find the graphic with the number that you get, memorize the graphic and then click the crystal ball. You will find, the graphic reflects in the ball is what you memorized.