Error analysis is an excellent way to reinforce concepts, as well as being an engaging activity. Systems of equations tends to be one of the more frustrating algebra topics for students due to the number of steps involved, the requirement to think through each problem individually (they take so many different forms) and the fact that even the tiniest error can spread through all the subsequent steps.
This worksheet would work best after all of the methods have been taught and the students are ready to "mix them up" a bit. The first six questions the student is asked to identify the best method for solving each system. The remaining problems each feature a system being worked out step by step, but when the check is performed it becomes apparent that something is wrong. (sooooo frustrating!!) Students must go back through the steps, determine where it went wrong, and fix the problem from there forward.
Consists of two pages to fit on the front and back of one sheet of copy paper. A key is also included with the error described and everything that must be changed highlighted.