Here is some direction:

The thread below contains the ideas you need for the first part:

http://www.mathhelpforum.com/math-he...-function.html

For the second part, you should know how to get the pdf of Y/2 from the pdf of Y ...... And you should know that the pdf of the sum of two random variables is the convolution of their seperate pdf's.

To get the pdf of the random variable max(X, Y), use the same idea that I used in my reply to your question about showing

E(U) = 1/3.