Find the rank of the matrix
\overline{A}=\left|\begin{matrix} 1 & 4 & 5 \\ 2 & 6 & 8 \\ 3 & 7 & 22 \end{matrix} \right|This matrix can be reduced to an upper triangular matrix by elementary row operations (see the following):
\overline{A}=\left|\begin{matrix} 1 & 4 & 5 \\ 0 & 1 & 1 \\ 0 & 0 & 12 \end{matrix} \right|The rank of the matrix is 3.