#### Answer

The shortest side: $600$ ft.
The longest side: $1000$ ft.
The middle side: $800$ ft.

#### Work Step by Step

Let the shortest side be $x$ (ft).
The longest, then, is $2x-200$,
and the middle side is $(2x-200)-200=2x-400$
Their sum (perimeter) is (equals) 2400:
$x+(2x-200)+(2x-400)=2400$
$5x-600=2400$
$5x=3000$
$x=600$
The shortest: $600$ ft.
The longest = $2(600)-200=1000$ ft
The shortest = $2(600)-400=800$ ft.