Arectangular field has an area 28800 sq. meter. its length is twice as long as its width. what is the length of its sides?

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