Answer
90 volts
Work Step by Step
The back emf opposes the applied emf of 120 volts. The combined effect gives the net voltage across the motor, which is IR by Ohm's Law.
$$\epsilon_{applied}-\epsilon_{back}=IR$$
$$\epsilon_{back}=\epsilon_{applied}-IR$$
$$=120V-(8.20A)(3.65\Omega)=90V$$
