This middle school math activity is meant to be an engaging way for students to become more familiar with algebra and solving for variables. They will enjoy the puzzle-like nature of solving for the variables and be excited to unlock each successive key. All of these equation sets can be solved with either a bit of logic and reasoning, basic algebraic steps (substitution, isolating variables) or a combination of both, making it perfect for middle school students no matter what exposure they have already had to algebra. The activity can be done as individuals or as groups.
In addition to addressing Common Core math standards (6.EE.B.5, 6.EE.B.7,8.EE.C.7,8.EE.C.8,MP.2), it has a nice tie-in with social studies units on geography or Greece.