13 worksheets cover subtraction problems using numbers 0-12. There are three short quizzes per sheet. Each quiz had 11 problems for that particular number.
I used these to practice timed subtraction with my students. Giving them 1 minute per quiz, (starting all students on the 0's) they went on to the next quiz the next day if they got a 100 on it. They stayed on the 2's until it was mastered. I had a bulletin board in my classroom to track their progress.