## Elementary Linear Algebra 7th Edition

$$y=-2, \quad x=1.$$
To get the solution by Gauss elimination, we form the augmented matrix $$\left[ \begin {array}{cccc} 1&-2& 5 \\ 3&1&1 \end {array} \right] .$$ Multiply the first row by $-3$ and adding it to the second row, we get $$\left[ \begin {array}{cccc} 1&-2& 5 \\ 0&7&-14 \end {array} \right] .$$ By the back substitution we have $$y=-2, \quad x=1.$$