Hello physics community! This is my first post to PF and I hope to contribute much more as time goes on. I am having serious trouble understanding Thevenin and Norton equivalent circuits, more specifically on how to find a circuit's equivalent. It only seems appropriate that to find a circuits Thevenin or Norton resistance, you combine or reduce the resistors in the circuit down to one. However, this does not seem to work for many problems, and I realized I don't understand how to find an equivalent circuit at all. My professor said to find the Thevenin voltage, I was to measure the voltage across some output terminals in the circuit, but that gives me no indication on how to go about actually solving. Attached is a picture of some circuit I found and I am trying to find it's Thevenin equivalent. Any help or just an explanation of Thevenin/Norton equivalents would be greatly appreciated. Thanks!