This might be a simple problem, but I simply cannot wrap my head around it; I'm still learning about ideal op-amps and electronics in general.
The problem is:
I have tried solving it using the gain formula for an inverting op-amp configuration, which goes "Av = -(Rf/R1)".
I determined an equivalent resistance for the top 5 resistors (R||R + R||R + R = 2R) and divided that by the resistor at the inverted input, which that gave me an answer of -2, where it should be -8, according to my professor's solution.
What the hell am I doing wrong, help is greatly appreciated!