Final answer:
A Wheatstone bridge is balanced when the ratio of the resistances on one side is equal to the ratio on the other side. Using the given resistances, Rx does not match any provided options, suggesting a possible error in the question or options.
Step-by-step explanation:
When dealing with a Wheatstone bridge, the bridge is considered balanced when the ratio between the resistances in one branch (R1 and Rx) is equal to the ratio between the resistances in the other branch (R2 and R3). The general formula when the bridge is balanced is R1/Rx = R2/R3. Given that R1 = 80 ohms, R2 = 120 ohms, and R3 = 280 ohms, we can set up the equation:
80 / Rx = 120 / 280
Solving for Rx:
Rx = 80 * 280 / 120
Rx = 22400 / 120
Rx = 186.67 ohms
However, this value doesn't match any of the options provided in the question. It's possible that there was a typo or mistake in the information given or in the options. If we assume the correct value for R1, R2, or R3, then the value of Rx could match one of the options listed.