The power used by an electrical device can be written as [tex]P= \frac{V^2}{R} [/tex] where V is the potential difference applied to the device and R is the electrical resistance of the device.
In this problem, the power used is P=590 W and the device operates at voltage of V=120 V, therefore we can re-arrange the previous equation to calculate its resistance: [tex]R= \frac{V^2}{P}= \frac{(120V)^2}{590 W}= 24.4 \Omega[/tex]
