Question 607723
<pre>
x-3y+2z=-21
   y-2z=12
      z=2 
</pre>


Convert to matrix form:


<pre>


 1  	 -3  	 2  	 -21 
 0  	 1  	 -2  	 12 
 0  	 0  	 1  	 2 

</pre>


Now add 2 times the 3rd row to the 2nd row (and replace the second row with this result)


<pre>


 1  	 -3  	 2  	 -21 
 0  	 1  	 0  	 16 
 0  	 0  	 1  	 2 

</pre>


Then add -2 times the 3rd row to the 1st row (and replace the first row with this result)


<pre>

 1  	 -3  	 0  	 -25 
 0  	 1  	 0  	 16 
 0  	 0  	 1  	 2 

</pre>


Finally, add 3 times the 2nd row to the 1st row (and replace the first row with this result)


<pre>

 1  	 0  	 0  	 23 
 0  	 1  	 0  	 16 
 0  	 0  	 1  	 2 

</pre>


The right hand column represents the solutions. So the solutions are x = 23, y = 16 and z = 2