let
x----------> length of the long side of rectangle
y---------> length of the short side of rectangle
P----------> perimeter of rectangle
we know that
x=5y-------------> equation 1
P=2x+2y---------> 72=2x+2y---------> equation 2
then
I substitute 1 in 2
72=2*(5y)+2y----------> 72=10y+2y----------> y=72/12---------> y=6
the answer is
the length of the short side of rectangle is 6 m
