One student will solve the problems in one column and their partner will solve the problems in the other column. Their answers should match. If they match, they can move onto the next problem together. If they do not match, they will check over each others work to try to find the error.
Every time I have done this activity, it has been a success. Students are motivated to find each others errors and get very excited when their answers finally match! Students become the teachers! It's fun to watch students work together and help each other understand order of operations.