Suppose That You Are Solving a System of Three Linear $$\left[ \begin{array} { r r r | r } 1 & 7 & - 4 & 9 \\0 & 1 & 20 & 4 \\0 & 8 & 6 & - 9\end{array} \right]$$

Multiple Choice

Suppose that you are solving a system of three linear equations by the Gauss-Jordan method and obtain the following augmented matrix. $$\left[ \begin{array} { r r r | r } 1 & 7 & - 4 & 9 \\0 & 1 & 20 & 4 \\0 & 8 & 6 & - 9\end{array} \right]$$
What row transformation would you perform next?

A) Multiply row 3 by $\frac { 1 } { 6 }$ .
B) Add $- 8$ times row 1 to 7 times row 3 .
C) Add $- 8$ times row 2 to row 3 .
D) Add $\frac { 1 } { 8 }$ times row 2 to row 3 .