Here are four different levels that focus on adding and subtracting within 20. Each level progresses and becomes harder. Purple is the easiest that adds single digit numbers and subtracts a single digit number from a double digit number. The blue level is the next level which contains harder adding and subtracting problems. The green cards students need to find the unknown addend. The red cards are story problems. Each level contains 12 different task cards, an answer key and a student answer sheet.