Where Should the Pivot Point Be Placed to Balance a Seesaw?

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To balance the seesaw with a 70kg adult on one end and a 30kg child on the other, the pivot point must be strategically placed. The adult exerts a force of 686N, while the child exerts 294N, and the board itself contributes 147N. By defining the distance from the pivot to the child as 'x', the distance to the adult becomes '10m - x'. Using the torque equilibrium equation, one can solve for 'x' to find the correct pivot point for balance. This approach ensures the seesaw remains level despite the differing weights.
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A 70kg adult sits at one end of a 10m board, on other end sits a 30kg child. where should pivot point be placed so board is balanced? board's mass is 15kg.

so far, i have pivot point is 15kg(9.8)=147N (5) <-- half the board length.. for adult i have 686N and kid is 294N. i know that Etorqueccw=Etorquecw ... but I am not sure how to use that for the lengths of both humans, since there are 2 variables. need two eqns then rite? but what's the other eqn?..:confused:
 
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You (should) have one equation and one unknown. Basically, suppose x is the distance from the pivot point the child. Then the distance to the adult from the pivot point is L - x where L is the length of the board. Put it into your torque equation and solve for x.
 

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