Question 191482
<pre><font size = 4 color = "indigo"><b>

               A     X  =  B 
          [ 1  2  5][x]   [2]
          [ 2  3  8][y] = [3]
          [-1  1  2][z]   [3]

Left multiply both sides by A<sup>-1</sup>

    A<sup>-1</sup>        A     X  =     A<sup>-1</sup>    B 
[ 2 -1 -1][ 1  2  5][x]   [ 2 -1 -1][2]
[12 -7 -2][ 2  3  8][y] = [12 -7 -2][3]
[-5  3  1][-1  1  2][z]   [-5  3  1][3]


               I     X  =  A<sup>-1</sup>B 
          [ 1  0  0][x]   [-2]
          [ 0  1  0][y] = [-3]
          [ 0  0  1][z]   [ 2]

                     X  =  A<sup>-1</sup>B 
                    [x]   [-2]
                    [y] = [-3]
                    [z]   [ 2]

Therefore x=-2, y=-3, z=2

Edwin</pre>