Help with rotational equilibrium torque questions?

[MrNeuro]

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I'm getting SLAUGHTERED on all these questions regarding torque @ equilibrium

im unsure as to what steps to take to get them right the specific step that messes me up is setting the rotational axis i have NO idea where to set it....i know that when you have a board with tension set the rotational axis to the point where tension is and i also know that if theres a fulcrum set it to the fulcrum however theres a couple questions in EK 1001 and EK physics that i have NO IDEA where to start from example

EK 304

A 10 m board with a mass of 15 kg rests on a large stationary block as shown. A 75 kg box is positioned so that its center of gravity is one meter from the right end of the board. what distance x could a 60 kg woman walk from the right end of the board before it falls. The picture also shows that from the end of the board to the end of the block it is 3m.

The picture...

i don't get why they set the rotational axis to the tip of the stationary block??? i mean then the go on to say that you can theoretically set it to anywhere u want but then have to consider the normal force, mass of the women, and mass of the board???? i don't get any of this someone please help!!

 

[Pisiform]

I mean where else would you set it. Like if the board falls, it going to rotate around the edge so taking the edge as the pivot seems fine. And you are still taking into account all the forces they gave you. Just do sum of clockwise moment = sum of anticlockwise

750 * 2 = (150 * 2 ) + (600 * x)

x = 2 m ... and add that 3m .... so it will give you 5m ,,,