Centre of Mass of Rigid Bodies — Prelims Questions

Three particles of masses $1\,\text{kg}$, $2\,\text{kg}$, and $3\,\text{kg}$ are placed at the vertices of an equilateral triangle of side $a$. If the $1\,\text{kg}$ mass is at the origin $(0,0)$ and the $2\,\text{kg}$ mass is at $(a,0)$, what are the coordinates of the center of mass of the system?