Content-rich math cards do their job, teaching students new skills in a fun way. This educational aid develops basic subtraction skills 13-18. Self-checking, answers on card backs. Sturdy cards and storage box. Students will delight in mastering new skills. No-see-through cards with quick-sorting, rounded corners. Details:White & black cards 3" x 6"Includes 1 box of 99 cardsFurther develop subtraction skills, practicing 13-18Great for test prep and reviewSelf-checking, with answers on card backsSturdy tagboard cards and reinforced cardboard storage box Ideal for teaching ages 6 and up