Equilibrium Constant Problem

[s3a]

Question:
http://img40.imageshack.us/img40/6341/questione.jpg

Answer:
http://img61.imageshack.us/img61/426/answer.jpg

The solutions seem completely wrong to me.

Anyways, so what I did is:

Kc = ([N2]^2[H20]^6)/([NH3]^4[O2]^3)

If I had the value of H20 to insert, I would be able to do this problem, but I don't know how to find the amount of H20. Does it have something to do with molar ratio?

Any help would be GREATLY appreciated!
Thanks in advance!

[Russ]

It does indeed have something to do with Molar ratio.
Draw up a chart that has a column for:

[initial amount]
[change in amount]
[amount at equilibrium]
[concentration at equilibrium]

Fill in what you KNOW from the question, then you can work backwards/forwards to fill in the blanks and solve it.