Question 1054231
So you fold up a square of size, X, from each edge. 
Let's call the left over part A on the width and B on the length so that,
{{{X+A+X=11}}}
{{{X+B+X=14}}}
.
.
{{{2X+A=11}}}
{{{2X+B=14}}}
and the area of the bottom,
{{{AB=80}}}
So from the length and width,
{{{A=11-2X}}}
{{{B=14-2X}}}
Substituting,
{{{(11-2X)(14-2X)=80}}}
{{{4X^2-50X+154=80}}}
{{{4X^2-50X+74=0}}}
{{{2X^2-25X+37=0}}}
Complete the square,
{{{2(X^2-(25/2)X)+37=0}}}
{{{2(X^2-(25/2)X+(25/4)^2)+37=2(25/4)^2}}}
{{{(X-(25/4))^2=625/16-296/16}}}
{{{(X-(25/4))^2=329/16}}}
{{{X-25/4=0 +-sqrt(329)/4}}}
{{{X=25/4 +- sqrt(329)/4}}}
Although there are two answers, we are limited by,
{{{A>0}}}
{{{B>0}}}
which leads to the solution,
{{{X=25/4-sqrt(329)/4}}}