Consider image below. The weight of the fire-fighter is 840 N. What is the torque of the fire-fighter's weight about P and what is the value of the force C which cancels out the torque?
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The answer to both your questions are hinted at or can be worked out from the equation: (Horizontal_Force_C) x 12m = (FF_weight) x 5m. You get this equation by summing up the moments around P and setting that sum = 0. You could pick any number of points about which to sum these moments, but point 'P' is the obvious choice for ease of setting up the problem and performing calculations.