By definition, the perimeter of a rectangle is given by:

Where,
w: width of the rectangle
l: length of the rectangle
We write then the inequality that represents the problem:

Rewriting we have:

Then, solving the inequality for "l" we have:


Therefore, the length must be at least 38 feet.
Answer:
An inequality that represents all possible values for the length of the deck is:

The possible values for the length of the deck is:
[38, inf)