Enter values for the matrix.
Enter fractions with a slash, as "3/4" or "-10/3".

### Add multiples of the row containing the red 1 to make the rest of the column zeros.

$$\left[\begin{array}{rrr|r}\large\color{Red} {1} & -3 & -5 & -18 \\ -2 & -4 & 1 & 21 \\ -1 & -1 & -3 & -10\end{array}\right]\begin{array}{ll}\large\phantom{1} & \\ \phantom{1} & \\ \phantom{1} & \end{array}$$