I think the value on this one would actually be something that is not listed as an answer choice! Haha, did it give you like a fill in the blank option or something like that?
In terms of the solving what you want to do is set up a general equation for the Perimeter and Area. For this one that would be
Perimeter = 2 * (length + width)
Area = length x width
Since we know that l = 3w from the information in the question you can substitute to get
P = 2(3w + w) = 8w
Setting equal to 48 means that 8w = 48
So w = 6 and l = 3 x 6 = 18
Putting that all together then would give an Area value of
Area = 18 x 6 = 108
I hope that helps get you moving in the right direction! Feel free to reach out if you have any more questions beyond that :)