Since power = current x voltage, you would divide the power (watts) by the voltage. The answer would be 1/10 amps or .10 amps.
Power = Voltage * Current
or I=P/V So the current in amps is equal to 12watts/120Volts = .1 amps
Power in watts = current x voltage
Rearranged, current = power/voltage
So in this example, current = 12/120
Current = 0.1 amps
should be 0.1Amp