Equivalent circuit of resistor in parallel with inductor
The net parallel impedance, Z is the product of the two impedances divided by their sum: -

Z = \$\dfrac{j 300\times 600}{600 + j300}\$ 

To evaluate this it is advisable to multiply the denominator by its complex conjugate: -

Z = \$\dfrac{j180000 \times (600 - j300)}{600^2 + 300^2}\$

This now equals \$\dfrac{54\times 10^6 + j108\times 10^6}{450000}\$

And, dividing through by 45000 yields: -


real part is 120 ohms and 
imaginary part is 240 ohms


This is equivalent to a resistor of 120 ohms in series with an inductance having a reactance of 240 ohms.