Two brothers, Jimmy and Robbie, sit 3.00 m apart on a horizontal seesaw with its fulcrum exactly midway between them. Jimmy sits on the left side, and his mass is 42.5 kg. Robbie's mass is 37.0 kg. Their sister Betty sits at the exact point on the seesaw so that the entire system is balanced. If Betty is 29.8 kg, at what location should she sit? Take the fulcrum to be the origin, and right to be positive. Assume that the mass of the seesaw is negligible.