The center of mass is the single point where the entire mass of the system can be treated as concentrated for purposes of translational motion.
In 2D space, a net external force on the system makes the center of mass accelerate exactly as if it were a single particle with the total mass at that point.
If all masses were equal, the center of mass would sit at the simple geometric center. The heavier a mass, the more it pulls the center of mass toward its position.
Next stepTo check your result: mentally picture the heaviest mass - the center of mass should be closer to it than to any lighter mass.