I am doing a class of statistics and prob and not a math major! struggling horribly.

I have 2 hw problems I need help getting started with. Any insight into the concept of Discrete RV would help too! Thanks for anyones time or help!

-Suppose a fair dice is tossed three times. Let X be the largest of the three faces to appear. Find px (k).

*I kno that the sum must be 216 if it was 6 each time, but I don't know how to present that in this concept.

-Suppose x is a binomial random number with n=4 and p=2/3. What is the pdf of 2X+1?

*I have no idea how to start this or what the PDF really is?

Any help would really be appreciated! I have a test this Thursday and I am really stuck!