Students are presented with 20 algebra problems and incorrect solutions. They are asked to provide the correct answer and explain what went wrong. The mistakes presented are what I have frequently observed in my years in the classroom.
The topics include: simplifying exponential and radical expressions (easy), finding slope from two points, graphing slope-intercept form, and basic operations with polynomials.
This is appropriate for younger students first learning these concepts or for older students that make these common mistakes in Algebra I or beyond.