Suppose we were given the following matrix (I made up the numbers). The first and second row are in row echelon form. However the third is not. Do we still need to put the third row in row echelon form even if we can see that 1 * x = 2, which we could solve for x??
$$ \begin{pmatrix} 1&5&5\\ 0&1&9\\ 1&0&2\\ \end{pmatrix} $$