<PRE><B>Question 1140346</B>
&lt;br&gt;
The problem tells you the variables to use:
x = amount at 8%
y = amount at 10%
z = amount at 12%&lt;br&gt;
(1) &quot;A person invested $6,700...&quot;  --&gt;  x+y+z = 6700&lt;br&gt;
(2) &quot;The total annual income from these investments was $716.&quot;  --&gt;  .08x+.10y+.12z = 716&lt;br&gt;
(3) &quot;The amount of money invested at 12% was $300 more than the amount invested at 8% and 10% combined.&quot;  --&gt;  z = x+y+300&lt;br&gt;
(a) The three equations are&lt;br&gt;
x+y+z = 6700
.08x+.10y+.12z = 716
z = x+y+300&lt;br&gt;
(b) For solving the system using matrices, the equations must be in the form Ax+By+Cz = D.  Two of the three equations are already in that form; you need to do a bit of work on the third one.&lt;br&gt;
Then the augmented matrix is the coefficients of the three equations....</PRE>