Answer
The equilibrium will shift to the right, increasing the concentration of $CO$.
Work Step by Step
Lower pressure at constant temperature means greater volume.
According to Le Chatelier's principle, a system with greater volume will favor the side with most amount of moles of gases.
Reactants: 1
Products: 2
*Note that C is a solid in this reaction, so it does not count.
Therefore, the equilibrium will shift to the right.
