This consists of a lesson plan, task cards, and answers to the task cards. This activity takes 20-30 minutes and is intended for students who already know how to add and subtract multi-digit numbers. Each student is to solve two questions independently. The two equations for each student result in the same answer, so students will know that they need to go back and check their work if their answers are not the same.
I put stickers on top of everybody's task card, so after they solved independently, they were to switch papers with their sticker partner and check their work. After, I grouped everybody by number and they were to double check and make sure they solved it correctly.