Let x mol of CO react so by stoichiometry x mol of H2O react, and x mol of CO2 and H2 formed

So at Equilibrium, We have the following

CO2  __________________________ x mol/l

H2    __________________________ x mol/l

CO   ___________________________  0.1-x mol/l

H2O ___________________________ 1-x mol/l

Therefore  

                     k=[CO2][H2]/[CO][H2O]

                   4.24=x^2/(1-x)^2

                         x=0.067 mol/l