Gas Pressure Puzzle

When Spaz crash lands he find himself in the dark sorrounded by ruble. On the wall ahead of him he can barely make out a set of levers which seems to control the flow of natural gas through some nearby pipes.

On closer inspection Spaz sees a maintenance tag that indicates the levers must be position to add up to twelve psi by moving them up, to add the labeled pressure, and down, to reduce by the labeled pressure.

This is the first puzzle the the player will encounter in the game so we've gone with a simple math puzzle to start them off.