I am trying to help my brother (in high school) understand how to solve rotational equilibrium problems. What he needs is an explanation on how to approach these problems. I understand each problem is different, but I imagine there must be a general method for solving them. I have put a problem below so that hopefully you could apply the explanation/method to an example to clarify things. Thank you.

Problem:

1) A uniform bridge 20.0 m long and weighing 4.00x10^5 N is supported by two pillars located 3.00 m from each end. If a 1.96x10^4 N car is parked 8.00 m from one end of the bridge, how much force does each pillar exert?

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This solution is provided in a 3 page .pdf file as well as a .doc file. It uses weight of the car and bridge to find force using a diagram of the system.

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The asking problem:
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Please help with the following problem. Provide detailed calculations.
A scale is attached to the ceiling and a mass of 1.00 kg hangs from it. It reads 9.81 N. Another identical scale at the right is connected by perfect strings passing over perfect pulleys to two 1.00 kg masses hanging vertically at the end of the strings (