Question 1171377
<pre>
Hank           h
Laura          L     h+n-1
Ned            n     3h
SUM           15
</pre>
{{{system(h+L+n=15,L=h+n-1,n=3h)}}}


{{{system(h+L+n=15,h-L+n=1,3h+0-n=0)}}}----------This may be a way to start, if you insist on matrix.   (Easier to solve without matrices).