Question 664361
To make a tree, you start with S, D, U, X as 4 separate branches. Then off of each branch, you add 3 more branches of whatever letter you took.


For example, off the 'S' branch, you add the letters 'D', 'U', and 'X' as 3 additional branches.


This will give you the following tree diagram


<img src="http://i150.photobucket.com/albums/s91/jim_thompson5910/Algebra%20dot%20com/10-10-201212-23-48PM.png">