This is one of a series of problems I created for my grade 7 math class a few years ago. Each of my students became an agent of the "SMS" (Special Math Service), and were hunting the archvillain, Dr. Ignoramus. Each problem was presented as a "mission" for them to complete. I present this one as a download for you to try at home.

This particular problem is an introduction to algebra, as Agents must balance an equation to open a locked door. An answer key is included.