This worksheet is a review worksheet that I use to "maintain" and keep one's brain fresh with past concepts so it is not forgotten. Constant review is necessary to make concepts become permanent. I will sometimes use this worksheet or one similar to teach a few new concepts. Don't worry if there are a few problems that have not been covered in-class yet. Don't count it for a grade or don't count those problems into the grade. A review worksheet similar to this needs to be done at least weekly, preferrably several times a week. If your students don't review, don't expect long term student achievement on statewide assessments. My scores are always the highest, not because I'm a good teacher, but because once we learn something we always re-visit it.