That will give you everything in terms of x.
Now just replace x with t.
For the last bit you'll have to solve for t when w=6 and then substitute that t in for the expressions for y and z. x of course is just t.
I'm not seeing w=(t-2)/2 from my hack at this so maybe check your work.
Post back some of your cut at this if you like and we can check for any mistakes.