Write the System of Linear Equations Represented by the Augmented $\left[ \begin{array} { r r r | r } 1 & 5 & - 8 & 4 \\ 0 & 1 & - 6 & - 4 \\ 0 & 0 & 1 & - 7 \end{array} \right]$

Multiple Choice

Write the system of linear equations represented by the augmented matrix. Use x, y, z, and, if necessary, w for the variables. Then use back-substitution to find the solution.
- $\left[ \begin{array} { r r r | r } 1 & 5 & - 8 & 4 \\ 0 & 1 & - 6 & - 4 \\ 0 & 0 & 1 & - 7 \end{array} \right]$

A) $\{ ( 178 , - 46 , - 7 ) \}$
B) $\{ ( 4 , - 4 , - 7 ) \}$
C) $\{ ( 6,1 , - 8 ) \}$
D) $\{ ( 250,38 , - 7 ) \}$