Answer
$\begin{vmatrix} 1 & 2 &-1 \\0 & -11 &19 \end{vmatrix}$
Work Step by Step
$\begin{vmatrix} 1 & 2 &-1 \\ 4 & -3 & 15 \end{vmatrix}$ $-4$times the first row is: $\begin{vmatrix} -4 & -8 &4 \end{vmatrix}$, thus adding this to the second row, it becomes: $\begin{vmatrix} 4-4 & -3-8 &15+4 \end{vmatrix}=\begin{vmatrix} 0 & -11 &19 \end{vmatrix}$, so the array becomes: $\begin{vmatrix} 1 & 2 &-1 \\0 & -11 &19 \end{vmatrix}$
