On a seesaw a 28-kg child sits 28 m from the pivot point

Question

I need expert help to solve the given problem:

Problem: On a seesaw, a 28-kg child sits 2.8 m from the pivot point.

Part A: Where should a 38-kg child sit to put the center of mass at the pivot?

I want help to find where a 38-kg child should sit to put the center of mass at the pivot.