I dont really know what to do to solve this problem. It wants me to find exact values of each part labeled with a variable.

I have the solution manual, but it doesnt go into any kind of depth, and sort of assumes that I know what its talking about, or how it got certain things. For example, it starts off by looking at variable y and states = y=(1/2)(9)

I dont know where the 1/2 comes from.

Can anyone give me some information? Usually a section in my book has an example to go along with it, this one doesnt. Please explain how you know something to be true in the process.