Suppose That You Are Solving a System of Three Linear $$\left[ \begin{array} { l r r r } 1 & - 12 & - 18 & 12 \\0 & 1 & - 5 & 10 \\0 & - 20 & - 11 & 3\end{array} \right]$$

Multiple Choice

Suppose that you are solving a system of three linear equations in three variables by the row echelon method ans obtain the following augmented matrix.
$$\left[ \begin{array} { l r r r } 1 & - 12 & - 18 & 12 \\0 & 1 & - 5 & 10 \\0 & - 20 & - 11 & 3\end{array} \right]$$
What row transformation would you perform next?

A) Add 20 times row 1 to $- 12$ times row 3 .
B) Multiply row 3 by $- \frac { 1 } { 11 }$ .
C) Add $- \frac { 1 } { 20 }$ times row 2 to row 3 .
D) Add 20 times row 2 to row $3 .$