Question 1099070
{{{L*W*H=340}}}
{{{W=5H}}}
{{{L=15+H}}}
Substituting,
{{{(15+H)(5H)H=340}}}
{{{H^2(H+15)=68}}
{{{ H^3+15H^2-68=0 }}}

{{{ (H-2)(H^2+17H+34)=0 }}}
Only positive roots are allowed.
{{{H-2=0}}}
{{{H=2}}}{{{in}}}
So then,
{{{W=5(2)}}}
{{{W=10}}}{{{in}}}
and
{{{L=15+2}}}
{{{L=17}}}{{{in}}}