Low-Pass and High-Pass Filters Outputs of Summing Amplifier
Alright. I'll open the gate to the path. And you're alone from this point on.

You can think of \$V_{sum}(t)\$ as a voltage source, because the summing amplifier has zero output impedance (in theory). So you can draw the two loops:







simulate this circuit &ndash; Schematic created using CircuitLab

Now you can put impedances and analyze the circuit. Note that the output voltages can be calculated from either KVL or KCL.