Answer
See the answer below.
Work Step by Step
For carbon monoxide:
$\sqrt{\bar{u^2}}=\sqrt{3RT/M}$
$\sqrt{\bar{u^2}}=\sqrt{3×8.314\ J/mol.K×298\ K/0.028\ kg/mol}$
$\sqrt{\bar{u^2}}=515.2\ m/s$
For argon, from Graham's Law:
$\sqrt{\dfrac{\bar{u_A^2}}{\bar{u_B^2}}}=\sqrt{\dfrac{M_B}{M_A}}$
$x/515.2\ m/s=\sqrt{28.0\ g/mol/39.948\ g/mol}$
$x=431.5\ m/s$
