House current is 120 volts. if a light bulb runs a current of 0.5 amps, what is the resistance of the bulb

Ohm's Law tells the relationship between voltage, current, and resistance.
It can be written in three different ways, depending on which ones you know,
and which one you want to find.

Here's the one we need:       

                           Resistance  =  (voltage) divided by (current)

                                               =  (120 V)  /  (0.5 Amp)

                                               =          240 ohms .