This is an excellent 20-25 minute activity which allows students with different skill levels to work at their own pace, and do problems comparable to their skill level.

This is order of operations, with the problems broken into 3 categories, easy (lights), medium (camera), hard (action).

The easy problems are worth 5 points each, the medium are 10 points each, and the hard are worth 15 points each.

Students must correctly work problems to obtain 30 points.

I usually print off a class set, and require the students to work the problems in their journal.