plz help to explain this problem?

Question

equilibrium constant Kc for the following reaction is 1.40.

H2(g) + CO2(g) <--> H2O(g) + CO(g)

Initially, 0.80 moles each of hydrogen gas and carbon dioxide gas are injected into a 1.00L flask. Calculate the concentration of the H2O(g) at equilibrium.

Answer 1

I'll point you to the right way:

x squared/(0.8 - x) squared = 1.4.

Now solve for x.