1. The problem statement, all variables and given/known data I'm having trouble trying to find equivalent resistance. Here's a picture of some circuits I am trying to simplify (link) For example, in circuit a, I can see that the 84 ohm and 105 ohm resistor are in series, and that can be simplified, but what do the markers A and B do to the circuit? Is the result of combining the 84 and 105 in parallel with the 63? And then what is the relationship of the 42 and the 21? Any tips on how to approach these problems are appreciated, thanks.