Answer:

Explanation:
Well, first off, let width = w, length = l and perimeter = P
P = 600
The width must be no more than 200 inches. Therefore,
w < 200
The length must be at least 2 times longer than the width. Therefore,
l ≥ 2w
What I would do is work back from the part about the length being two times as long as the width, because I don't think you'll be able to have more than 200 inches as a width even knowing that the perimeter is 600 and the length must be twice the width.
Formula for perimeter
P = 2l + 2w
Substitute the l for 2w to represent that the length is at least twice the width (l = 2w)
600 = 2(2w) + 2w
600 = 6w
100 = w (look above and check that this follows the inequality equation, w < 200)
The width can at the most be 100 inches.
If the width is 100 inches, according to the equation above (2w = l) we can assume that the length would be 200 inches.
l = 2w
l = 2(100)
l = 200
The dimensions would be 200 x 100