I have a 12V 0.14A pc fan which will be connected to a 35V power supply. Which resistor do I need to run the fan at 12V and and which resistor to run it at 7V (so it's more quiet).
Thanks for any help.
Thanks for any help.

That is not a good way to reduce the voltage to the fan. You are wasting energy in those resistors and the resistors will get hot.
You need to use a voltage regulator like a LM317. They are cheap and very easy to hook up and give you the option of varying the fan speed as well.
http://www.national.com/mpf/LM/LM317.htm…
An even better option would be to use a 12V power source.
If you still want to use resistors you need to use ohms law.
to run the fan at 12V you need a voltage drop over your resistor of 35  12 = 23V
with I = 0.14A then R = U/I = 23 / 0.14 = 164 ohm
to run the fan at 7V you need a voltage drop over your resistor of 35  7 = 28V
with I = 0.14A then R = U/I = 28 / 0.14 = 200 ohm
The values above are for the resistors in series with the fan.
You need to use a voltage regulator like a LM317. They are cheap and very easy to hook up and give you the option of varying the fan speed as well.
http://www.national.com/mpf/LM/LM317.htm…
An even better option would be to use a 12V power source.
If you still want to use resistors you need to use ohms law.
to run the fan at 12V you need a voltage drop over your resistor of 35  12 = 23V
with I = 0.14A then R = U/I = 23 / 0.14 = 164 ohm
to run the fan at 7V you need a voltage drop over your resistor of 35  7 = 28V
with I = 0.14A then R = U/I = 28 / 0.14 = 200 ohm
The values above are for the resistors in series with the fan.

go get a regulator IC or use voltage drop circuit