Hi, how do I work out the gain of this circuit? Thanks.

 

Here are two videos that describe easy ways to understand most op amp circuits. They should give you enough information to figure this out on your own:

http://www.youtube.com/watch?v=K03Rom3Cs28
and
http://www.youtube.com/watch?v=7FYHt5XviKc

 

First, you break the circuit into two parts.

The right op-amp is just a buffer. It seems to simply isolate the left op-amp circuit from the rest of the system. The rest of the system is not shown.

The left op-amp is an none-inverting configuration. So the Gain=1+(Rf/Rin). If I am not mistaken it looks like Gain=1+(10k/10k)=1+1=2.