Center of Gravity??

Question

Three particales are located in a coordinatet system...
The mass 3kg is located at the origin.
The mass 6kg is located 10 meters on the x coordinate, and the mass 9 kg is located 6 meters on the y coordinate.

Find the distance of the center of gravity from the origin.

Answer 1

Xc=sum of moments about y axis/ total mass
Yc=sum of moments about x axis/ total mass

total mass M=3 + 6 + 9=18
sum of moments about y axis= My
My=0x3 + 10x6 + 0x9=60
Xc=60/18=3.33

My= 0x3 + 0x6 + 6x9=54
Yc=54/18=3

Xc,Yc= (3.3, 3.0)