Question 1074737
y, length from end of garden to house


Two of the sides sum to {{{y+y=2y}}}.  The side opposite the house must finish the length of the fence material of 80; so  {{{80-2y}}} is this length.


The two dimensions are {{{y}}} and {{{80-2y}}}.
Area {{{A=y(80-2y)}}}.


Maximum area is when the rectangle becomes square shaped.
Since only three sides are to be used for the fence around the garden, each side is  {{{80/3=26&2/3}}} meters.