Let
x---------> the length side of rectangle
y---------> the width side of rectangle
we know that
x=2y-----> equation 1
area=x*y-------> 28800=x*y------> equation 2
substitute 1 in 2
28800=[2y]*y-----> 28800=2y²-------> y²=14400------> y=120 m
x=2*y----> x=2*120------> x=240 m
the answer is
the length side of rectangle is 240 m
the width side of rectangle is 120 m
