If there's no current through a battery, can it supply a voltage drop across a resistor?
If the current thru the power supply is zero, you can disconnect it. You can take out V2 and the circuit is unchanged.
The parallel of R2 and R3 is 200 Ohm. So the current thru V1 is 30mA (24V / (200&Omega; + 600&Omega;) ). The voltage drop thru R1 is 18V so the voltage on R2 and R3 is 6V, with or without V2.