Are you stuck on any part of this in particular? How much of this do you already understand and what do you need help with?
As a start :
1. You are given the sizes of the fragments P-S, what do you know about how DNA fragments separate when run like this?
2. Without seeing the info that this question (presumably) provides - is AAGCTT the site at which HindIII digests? If so, then how many times must it have digested to result in the number of DNA fragments that it did?
3. Does it tell you the size of the untreated DNA? (Probably not.) If not, estimate based on the size of P.
4. If one of the digestion sites changes, will the enzyme be able to digest it? Therefore how many fragments would there be?