alright im rather confused at the explanation of the ohms law stuff.
Your calculations are correct. I though you were using a standard 80mm or 120 mm fan. A fan of single digit watts to cool a computer. This is a 10 watt fan.
The 10 ohm 10 watt resistor is (was) available in Radio Shack. It will be about as warm as a standard 7 watt Christmas tree light.
You could also so same with a 7812 single chip power supply. Might also still be sold in Radio Shack. But due to high current, the supply chip must be mounted on some metal for cooling. Otherwise would go into protective overheat protection mode. Again, to learn. Routine are for many electronics devices (power supply chips, Intel CPUs, etc) to protect themselves from overheating with no damage.
Apppreciate that your numbers have completely changed the whole problem. Yes you could use the 10 ohm 10 watt resistor. But your problem is approaches limits, for example, on that single chip power supply solution. You will feel things get warm (and well within safe operation even though it feels warm). And to appreciate how much heat is 6 watts.
If a 12 volt fand creates 20 volts spikes, that is perfectly normal and acceptable operation. No acceptable fan will create spikes that destroy itself.
Assuming Radio Shack still sells that 10 ohm 10 watt resistor, then a quick purchase can result in a quick test.
BTW, getting confirmation of your math is simple. More fun is to discover math errors by creating smoke.