Two children are playing on a  feet long a seesaw.

Point masses of the children are  pounds and  pounds.

Assume that the child on the left end as the origin.

Thus, .

Child on sit right side is 10 feet away from the origin.

Therefore, .

Find the center of mass where the system is at the equilibrium.

.

Substitute , ,  and  in .

Center of mass at the  ft.

Center of mass at the  ft.