These number cards can be used for addition, subtraction, missing addends, or teaching number sentences. They are differentiated in three levels. The ones with butterflies on them are for beginners. The cards are numbered within 10. The next level ( monkeys and alligators) is for the average student. They are numbers within 20. The hippo set is for your advenced students. These numbers are within 30. I was amazed to see what my students could do with them. Some stuents were changing around the equal signs and some were creating missing addends in various positions.