I originally designed this activity for 7th grade students as fun way to review integers. It would also work well for an Algebra course, extra credit, or as emergency sub plans.
I work a few of the problems with the students and encourage them to "do all the math" first BEFORE trying to solve the Sudoku. There is an answer bank at the bottom of the sheet which students can use to ensure that they are doing the problems correctly.
When they finish all of the problems, I check their work (to ensure that ALL of my students have the correct answers) prior to solving the puzzle. Then, I let them solve the Sudoku for extra credit.
Students really get into this lesson as they like the challenge of trying something new. The Sudoku adds a fun challenging twist to the review.