Answer
The center of gravity of the system is (1.3, 0.9, 0).
Work Step by Step
$
m = 2+5+2+1 = 10 \\
\bar{v} = {1 \over 10} \left(
2 \cdot \begin{bmatrix} 5 \\ -4 \\ 3 \end{bmatrix}
+ 5 \cdot \begin{bmatrix} 4 \\ 3 \\ -2 \end{bmatrix}
+ 2 \cdot \begin{bmatrix} -4 \\ -3 \\ -1 \end{bmatrix}
+ 1 \cdot \begin{bmatrix} -9 \\ 8 \\ 6 \end{bmatrix}
\right) \\
= {1 \over 10} \left(
\begin{bmatrix} 10 \\ -8 \\ 6 \end{bmatrix}
+ \begin{bmatrix} 20 \\ 15 \\ -10 \end{bmatrix}
+ \begin{bmatrix} -8 \\ -6 \\ -2 \end{bmatrix}
+ \begin{bmatrix} -9 \\ 8 \\ 6 \end{bmatrix}
\right) \\
= {1 \over 10} \cdot \begin{bmatrix} 13 \\ 9 \\ 0 \end{bmatrix} \\
= \begin{bmatrix} 1.3 \\ 0.9 \\ 0 \end{bmatrix}
$
$\therefore$ The center of gravity of the system is (1.3, 0.9, 0)
