I am having difficulty in formally proving a simple argument. Consider

P(x) v Q(x)
not P(x)
----------
Q(x)

It is easy to see that the argument is indeed valid, but I cannot seem to prove it formally. Here is one attempt:

P(x) v Q(x)
not P(x)
-----------
|| P(x)
| ----
|| _|_     _|_ intro 2,3
|   
|
|| Q(x)
| ----
|| ??
|??
---------
Q(x)

I am obviously stuck on a basic proof, and I would appreciate any pointers. I am used to the Fitch style notation and make use of an application called 'Fitch' to do formal proofs, so I would appreciate guidance in the parlance of Fitch.