1. The problem statement, all variables and given/known data Calculate the resistance of R3 so that Vab = Va - Vb = 0, assume Rth is 75Ω. Here is a picture of the circuit: http://i.imgur.com/zsQBYJx.jpg 2. Relevant equations 3. The attempt at a solution Never seen this circuit before, don't know where to begin. I assume I have to analyze the voltage at each node and set up a system of equations which can allow me to calculate R3 based off of the values that I already know, but i'm not sure how to begin. Thanks in advance for any hints.