This activity has been wildly successful in my classroom with my 7th and 8th grade students. There are several equations with individual tiles to show the steps to solve each equation. Every tile must be used for the puzzle--if students have left over pieces, they know to correct a mistake; if students need extra pieces, they know to correct a mistake! It is a great check before the end of a unit on one-step equations (there is one two-step equation)! It can also be used to scaffold the process for learners who are not understanding the concept.