Trend® Skill Drill Flash Cards. Subtraction 0-12 flash cards are great for practicing and mastering subtraction to prepare for higher-level math concepts and success. Practice math with 91 self-checking cards. Activity ideas are included to keep kids engaged and challenged in classrooms, homeschools, learning centers and more. Cards show equations on one end and answers on the other. 91 flash cards included, 3" x 6" each.