Question 896654
More than one answer.
Three sides.
L for length
w for width
L=3w.


{{{w+2L=120}}}
{{{w+2*3w=120}}}
{{{7w=120}}}
{{{highlight(w=17.1)}}} meters and {{{highlight(L=51.4)}}} meters.


Alternative:
{{{2w+L=120}}}
{{{2w+3w=120}}}
{{{5w=120}}}
{{{w=120/5}}}
{{{highlight(w=24)}}}  and from that, {{{highlight(L=72)}}} meters.



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Fixed Earlier Mistake