What is the reactance when the frequency is 80 kHz?
The pedantic and reasonably correct answer is 0.29256423362 ohms reactive and given that you got 0.29 ohms I would suggest that your instructor got the wrong answer or you have not fully stated what the question was.

There is a possibility that the answer expected was -0.29 ohms (as opposed to an inductor that has a positive value). See this from wiki: -