Perimeter of a rectangle is twice the length plus twice the width or
2W + 2L = Perimeter
where W = width and L = length
Per the description the length = 2w - 3
2W + 2(2W - 3) = 24
2W + 4W - 6 = 24
6W - 6 = 24
6W = 30
W = 30 / 6
W = 5
So your width is 5 feet.
Plug in this result to the length equation:
2(5) - 3
10 - 3
7 = L
Your length is 7 feet.
