Resistor Network with voltage source and current source
R3 is in parallel with Vs hence it plays no part in solving the problem. Next, convert Vs and R1 to a current source: -



So now you have two current sources in parallel and the total current is the numerical sum of the individual current sources. You also have R1 and R2 both in parallel with the combined current source (easy life). So what voltage is produced by the combined current source into R1||R2?

That will be Vout.