Final answer:
The resistance of the resistor is 18.0 Ohms.
Step-by-step explanation:
The resistance of the resistor can be calculated using Ohm's law, which states that the resistance (R) is equal to the voltage (V) divided by the current (I). In this case, the voltage is 9.0 V and the current is 0.50 A, so the resistance can be calculated as:
R = V/I = 9.0 V / 0.50 A = 18.0 Ohms
Therefore, the resistance of the resistor is 18.0 Ohms.