concentration of carbon monoxide at equilibrium

Question

Knowing Kp = Kc(RT)Δng (R=0.0821 L atm/mol K)

The reaction

2CO2 (g) ↔2CO(g) + O2 (g)

has Kc = 6.4 ×10−7.

If a 1.00 L container holding 1.0 ×10−2 mol of carbon dioxide is heated to 2000 Celsius and decomposes, what will be the concentration of carbon monoxide at equilibrium?

Answer 1

2CO₂(g) <===> 2CO(g) + O₂(g)

0.01......................0..............0.......Initial

-2x.......................+2x..........+x......Change

0.01-2x..................2x............x.......Equilibrium

Kc = [CO]²[O₂] / [CO₂]²

6.4x10^-7 = (2x)²(x) / (0.01-2x)²

6.4x10^-7 = 4x³ / 4x² - 0.04x + 1x10^-4

Solve for x (too much math for me) and multiply that value by 2 to get the equilibrium concentration of CO.