can someone please help. I keep getting the answer wrong. I know I have to use the quadratic formula at the end, and I think that's my biggest problem. Can someone explain this to me step by step please? Consider 1.60 mol of carbon monoxide and 3.60 mol of chlorine sealed in a 8.00 L container at 476 oC. The equilibrium constant, Kc, is 2.50 (in M-1) for

CO(g) + Cl2(g) ↔ COCl2(g)

Calculate the equilibrium molar concentration of CO.

Question

can someone  please help.  I keep getting the answer wrong. I know I have to use the quadratic formula at the end, and I think that's my biggest problem. Can someone explain this to me step by step please? Consider 1.60 mol of carbon monoxide and 3.60 mol of chlorine sealed in a 8.00 L container at 476 oC. The equilibrium constant, Kc, is 2.50 (in M-1) for 

CO(g) + Cl2(g) ↔ COCl2(g) 

Calculate the equilibrium molar concentration of CO.