Add multiples of the row containing the red 1 to make the rest of the column zeros.
\(\left[\begin{array}{rrr|r}\large\color{Red} {1} & 2 & 4 & -3 \\
-4 & -4 & -1 & -25 \\
1 & 4 & -5 & 28\end{array}\right]\begin{array}{ll}\large\phantom{1} & \\
\phantom{1} & \\
\phantom{1} & \end{array}\)