Question 718533
Original length of each side, x.

{{{(x-5)(x-6)=6}}}, only shows the area of the rectangle after shortening side lengths of the original x by x square.


x^2-11x+30=6
x^2-11x+24=0
{{{(x-3)(x-8)=0}}}


x would make no sense if it were 3.  Only {{{highlight(x=8)}}} makes any sense.
Check:  (8-6)(8-5)=2*3=6