How to find V,and I on this circuit

here is the image.see this to understand the problem better.
http://oi52.tinypic.com/10pypw9.jpg
how to find I2,I3 and V from this?

What you need is ohms law and Kirchhoff's law

I1 = I2 + I3 (conservation of charge)
Also, I2 = 3 I3 because both resistors see the same voltage and the current is inversely proportional to the resistance (smaller resistance = larger current) U/R = I ohms law

So we have I1 = 3 I3 + I3 = 4 I3 --> I3 = 8/4 = 2A which means I2 = 6A

The total voltage is the drop over the 4 ohm resistor + drop over R2 (or R3)
So the total drop is I1 4 + I2 20 = 8 4 + 6 20 = 32 + 120 = 152V

You can check the answer by using ohms law again:

current through R2 = Ur2 / R2 = (152 - 8 4) / 20 = 6A which is what we found earlier.

note: in my math I use a b to denote a * b (multiply) to reduce clutter.