This question should be easy but I just can't make it make sense

2.00 moles of methane and 1.00 moles of steam are allowed to reach equilibrium in a 1.00dm³ container. At equilibrium 0.66 mol steam remains.
Calculate a value for the equilibrium constant and give its units.
CH4 (g)+ H2O (g)⇌ 3H2(g) + CO(g) ∆rH = +206kJ mol-1

I know how to calculate KC once I have the moles and the mark scheme just does not help at all with calculating the moles of each substance.

Initially, there are 2.00 moles of methane, 1.00 moles of steam, 0.00 moles of H2 and 0.00 moles of carbon monoxide.

It tells you that at equilibrium, there are 0.66 moles of steam left, so the moles of steam that have reacted = 1.00 - 0.66 = 0.34 mol. Since steam and methane react in a 1:1 mole ratio, that is also the number of moles of methane that have reacted. Can you now work out how many moles of methane are left?