At Sifu Faiza's Kung Fu School, kids learn to be strong and fast. They also learn to be smart, cool-headed, and honest. So Joy, Adam, Sam, and Amy are surprised when the key to the school is stolenâas well as all their kung fu gear. Now they'll have to use all kinds of calculationsâaddition, subtraction, multiplication, and divisionâto figure out the clues, follow the thieves, and find . . . The Lost Key.