Question about AC-RL circuit
First, find the current in the inductor, keeping in mind its phase relationship with the current in the resistor. Here's a hint: It's 3 mA (not 1 mA). The problem was specially constructed to make this step easy. Can you explain why?

Next, knowing the voltage and current, calculate the AC impedance of the inductor.

Finally, knowing the impedance and the frequency, calculate the value of the inductor.