<PRE><B>Question 138195</B>
&lt;pre&gt;
First number:  x
Second number: y
Third number:  z


The sum of the 1st number and 2 times the third: &lt;b&gt;x + 2z&lt;/b&gt;
Then subtract the 2nd number &lt;b&gt;x + 2z - y&lt;/b&gt;, or &lt;b&gt;x - y + 2z&lt;/b&gt; to keep things in order.
The result is 1:  &lt;b&gt;x - y + 2z = 1&lt;/b&gt;


2 times the 1st number: &lt;b&gt;2x&lt;/b&gt;
Plus the 3rd number:    &lt;b&gt;2x + z&lt;/b&gt;
&#39;is&#39; means equals, so   &lt;b&gt;2x + z = 3&lt;/b&gt;


The 1st number, &lt;b&gt;x&lt;/b&gt;, plus 3 times the 2nd, &lt;b&gt;3y&lt;/b&gt;, plus the 3rd, &lt;b&gt;z&lt;/b&gt; 
is (=) &lt;b&gt;18&lt;/b&gt;, so:
&lt;b&gt;x + 3y + z = 18&lt;/b&gt;


So, here are your three equations.
&lt;b&gt; x -  y + 2z = 1&lt;/b&gt;
&lt;b&gt;2x      +  z = 3&lt;/b&gt;
&lt;b&gt; x + 3y +  z = 18&lt;/b&gt;


Looking at the coefficients, I would say that Gauss-Jordan elimination is the
best solution method.  But you do it however you like.</PRE>