Answer
$$
x_1
\begin{bmatrix}
4 \\ 1 \\ 8
\end{bmatrix}
+
x_2
\begin{bmatrix}
1 \\ -7 \\ 6
\end{bmatrix}
+
x_3
\begin{bmatrix}
3 \\ -2 \\ -5
\end{bmatrix}
=
\begin{bmatrix}
9 \\ 2 \\ 15
\end{bmatrix}
$$
Work Step by Step
The vector on the right hand side holds the constants from the right hand sides of each of the equations. The vectors multiplied by $x_1$, $x_2$ and $x_3$ hold the coefficients of each variable in the three equations.
