The equivalent resistance beyond the resistor R4 (i am coming from right to left on the circuit)is:
This gives you the following reduced circuit:
simulate this circuit – Schematic created using CircuitLab
Now the current through the R3 can be determined by applying current divider rule(consider going through this topic once) as:
You can find the current A3 to be 0.58mA.
Look at the question now and forget the reduced schematic.
The remaining 0.42mA current passes through R4 and it divides itself for R2 and R1. Apply current divider rule here as well:
Now the remaining of 0.336mA(=A1) current flows towards R1. Here you need to take negative of this current because the direction specified in the question is opposite to the direction it actually flows.
For the voltage V3, apply Ohm's Law. I will show you the solution of V3 and remaining one for you.