1. The problem statement, all variables and given/known data Hi, I'm trying to solve this problem on MasteringPhysics: This circuit is given, and it says C-eq for the circuit is 9.22 microfarads: http://img143.imageshack.us/img143/3475/walker4ech21pr118.jpg [Broken] The question is to find C in the figure knowing C-eq is 9.22 microfarads. 2. Relevant equations C-eq series = 1/C-eq = 1/C1 + 1/C2 + ... C-eq parallel = C1 + C2 + C3 ... 3. The attempt at a solution At first I tried to take the three center capacitors to be parallel (The 7.22, 4.25, and 8.35) and find the Ceq of them and then take the other two to be in a series with this C-eq. But when I do that, I get a negative value for C. Then I tried to take the C, 12.0 uF, and 8.35 uF to be in a series, combine them and then have that C-eq be parallel to the other two, but that also gives me a negative value. Thank you.