You need to simplify the circuit, and find the equivalent resistance of the entire circuit.

It helps if you look at it like this:




Start from the bottom, work up.

You have 4 ohm, 5 ohm, 3 ohm in series, so that equals one 12 ohm resistor. That 12 ohm resistor is in parallel with the 6 ohm resistor. I assume you know how to do parallel and series equivalent resistances...so the 12 ohm in parallel with the 6 ohm gives one equivalent resistor of 4 ohms. This 4 ohm resistor is in series with a 1 ohm, giving a 5 ohm equivalent. This 5 ohm is in parallel with a 2 ohm, which gives a 1.43 ohm equivalent. This is in series with a 3 ohm, which gives 4.43 ohms.

As for part b:

You know the current through the 5 ohm resistor is 1A, so you know the voltage difference through that section of the 3 resistors using ohms law....that voltage difference is 12V. The voltage difference across the 6 ohm resistor in parallel with that portion must be the same, so you can then determine the current through it also using ohms law, 2A. Add those 2 currents together, 3A, and you have the current going through the 1 ohm resistor. You then know this voltage difference also using ohms law, to be 3V across the 1 ohm resistor. Now you know the total voltage difference for that side of the circuit to be 15V. This must be the same across the 2 ohm resistor, so you know the current through that resistor to be 7.5A. Now you know the current going through the 3 ohm resistor on top to be 7.5A + 3A = 10.5A...and thus the voltage across it is 31.5V. Add this 31.5V to the bottom portion's 15V, and you get 46.5V.

If you need more help, my AIM screen name is Purespeedintegra.