The centre of masses of two particles with masses 2 kg and 1 kg located at (1,0,1) and (2,2,0) is located at :

4/3, 2/3, 2/3 2/3, 4/3, 2/3 2/3, 2/3, 4/3 1/3, 2/3, 2/3

4/3, 2/3, 2/3

Sum of masses = 2 + 1 = 3 x-coordinate : (2 x 1 + 1 x 2)/3 = 4/3 y-coordinate : (2 x 0 + 1 x 2)/3 = 2/3 z-coordinate : (2 x 1 + 1 x 0)/3 = 2/3.