Answer :
To solve the problem it is necessary to apply the concepts of Torque and equilibrium.
The Torque is defined as:
[tex]\tau= F*d[/tex]
Where
F= Force
d = Distance
In this particular case, the force is caused by the weight of both children.
In turn, when there is equilibrium, the two torques must be equal therefore
[tex]\tau_1 = \tau_2[/tex]
[tex]m_1gd_1 = m_2_gd_2[/tex]
[tex]m_1d_1 = m_2d_2[/tex]
Replacing with our values
[tex](36)(1.2)=(24)d_2[/tex]
Re-arrange to find [tex]d_2[/tex]
[tex]d_2 = \frac{(36)(1.2)}{24}[/tex]
[tex]d_2 = 1.8m[/tex]
Therefore the distance that the second kid should sit to balance the see-saw is 1.8m from the pivot.