How do i solve this chemistry problem?

A 2.000 gram sample containing graphite (carbon) and an inert substance was burned in oxygen and produced a mixture of carbon dioxide and carbon monoxide in the mole ratio 2.00:1.00. The volume of oxygen used was 747.0 milliliter at 1,092K and 12.00 atmospheres pressure. Calculate the percentage by weight of graphite in the original mixture.