Need assistance with current limiting resistor for LED
It's entirely possible... and apparently math just wan't my thing yesterday. As a few others have pointed out since, the LEDs would take 11.9V, and a resistor to drop the remaining 100mV at 100mA is 1 ohm.

As far as the resistor itself, assuming one diode, we can do an example. The diode will drop 1.7V from the 12V source, leaving 10.3V to go away somehow (without a resistor this burns up the diode). The 10.3V happens to also be at 100mA, which will be very bright, but that's ok. Now, we just need a resistor that will drop 10.3V at 100mA, or 103 ohms. With that resistor, that diode, and the 12V source, voltages add to 0V, so everything's happy.