Circuit mesh analysis with 2 voltage sources
simulate this circuit &ndash; Schematic created using CircuitLab

You can use this diagram to understand the current direction and accordingly get correct loop equations. 


Decide the loop current direction.
Then mark voltage drop according to the current direction (current entering at a point is considered as positive).
Apply KVL, in the direction of loop current.


It can be seen from the diagram that currents flowing through R2(30 ohm) are actually adding up.
Now you can find out all currents and voltages at every node.