Here are 4 different level of word problems that focus on adding and subtracting within 20. The purple level has key words underlined and easier problems. The blue level increases in difficulty and doesn't have key words underlined. The green cards add three or four numbers together within 20. Finally, the red task cards are solving for the unknown addend. Each level has 12 cards, an answer key, and a student answer sheet. Total there is 48 cards! They make a great center and another way to differentiate in your classroom! Happy teaching!