Question 838809
A = L X W
Choose EITHER L or X, not both.  


Assign Variables:
(I will choose mine a little bit differently)
d = length of garden
d = 20 feet
w = width of garden
A = area of garden


Equations and Solution:

{{{A=d*w}}} and perimeter given as 64 feet means {{{2d+2w=64}}}.
We know what is the d value, so we want to solve for w.
-
{{{2w=64-2d}}}
{{{w=32-d}}}
{{{w=32-20}}}
{{{highlight(w=12)}}} feet
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FINDING AREA VALUE
{{{A=d*w}}}
{{{A=20*12}}}
{{{highlight(A=240)}}} square feet