For the first part:
if w is width and length is 2 times that, what would the length be?
For the second part:
we know that the perimeter is less-than 48in, so we can start by saying
something<48
next you have to determine what that something is: the perimeter.
To find perimeter, you add the length of the sides. We already know that there are two sides which measure 'w' units, and two sides which measures are the expression you're finding in the first part. So, you simply need to add these together!
width + width + length + length<48.
(Note: you'll obviously want to replace the words width and length with the values for the width and length; in the case of width, the value is given in the problem in the form of a variable, and the length is the expression you solve for in the first part.
You should be able to solve to find the expression from the first part on your own, and once you have those, simply plug the value of the width and the length into the expression. Rather than just giving you the answer, this allows you to still work it out on your own to a certain extent.
Make sense? (: