I've never tried to reduce a circuit before and I'm pretty sure I could do it, which means you certainly can. Thévenin's theorem - Wikipedia, the free encyclopedia
Provides many examples of how to calculate the Thevenin equivilent on circuits more complicated than what you linked.
for thenevin, you reduce the circuit to a single resistor and voltage source, for norton, it's again an equivalent resistor, and a current source equal to the total current. i leave it to you to arrive at the correct answers..... all you need to know here is how to calculate resistors in series or parallel, and how to calculate the current.
For the Thevenin voltage, calculate the voltage across the points where RL is connected with RL removed.
For the Thevenin resistance, remove the voltage source(s) and replace it (them) with a short circuit. Replace any current sources with an open circuit.Then calculate the resultant resistance. Imagine that you connected an Ohm meter across across the points where RL is connected with RL removed. The reading would be the Thevenin resistance.
For Norton, calculate the short circuit current. This is the Norton current. Calculate the resistance as I said above.
Once you have the equivalent circuits, it is then easy to calculate the currents & voltages.