Personally, I think the best thing to do is simplify it (just as you would with any algebra question), then once you've solved the complete circuit, work backwards from that to get the details.
For a start:
1) The two 15 ohm resistors are in series, so treat that at ONE 30 ohm resistor.
2) That then gives you two 30 ohm resistors in parallel, which equals 15 ohms.
3) That 15 ohms is in series with the 20 ohm resistor, giving a value of 35 ohms.
4) The 35 ohms is in parallel with the 10 ohm resistor, giving a total resistance for the circuit of 7.78 ohms (to two decimal places).
5) From ohms law this gives a voltage of 15.56V as the supply voltage (7.78x2).
6) Using ohms law again (15.56/35) gives roughly 0.444 amps current through the 20 ohm resistor.
7) This same current flows through the parallel 30 ohm resistors, so each 30 ohm resistor gets half the current = 0.222A.
8) As the 30 ohm 'resistor' we want is two 15 ohms in series, each will have the same current through them, so using ohms law again we get 3.3V across either 15 ohm (0.222x15).
I've worked this entirely for you (which as others will tell you ISN'T something I normally do!), but hopefully it will give you some insight in how to simplify such questions?.