The current going through the resistor R1 in the figure does not change whether the two switches S1 and S2 are both open or both closed. The resistances are R1 = 70.00 Ω, R2 = 50.00 Ω, and R3 = 62.00 Ω. The voltage is V = 15 V. With this information, what is the value of the unknown resistance R? Recall that a conducting wire can be treated as a resistor of 0 Ω, and points on a wire between resistors are at the same potential. Hint:
Kirchoff's rules are useful here.
The image is found here: http://www.chegg.com/homework-help/...itches-s1-s2-open-closed-resistances-q4890516
The Attempt at a Solution
I tried to add up all three resistors originally and got 182 ohms total, then made that equal to 50 + (70R)/(70+R) but it's not working. Not quite sure how to apply Kirchoff's rules here so any help would be appreciated.