Proper use of Solve App

[ebswift]

I'm at a point where I'm horribly confused with the solve app. I can get it to work for different things, but there is one scenario where I'm finding it tough to get right - a simple solve for 2 unknowns. I tried a method from this thread, but get a cannot solve message:

http://www.hpmuseum.org/cgi-sys/cgiwrap/...ead=258059

Export attempt from above:
   

symbolic view:
   

Cannot solve:
   

Now, the REALLY confusing part is that I got it working using X & Y variables. BUT, after playing with the l & w variables for a while I can't even get X & Y to solve anymore. I also mucked about using STO to no avail.

Please help with the solve workflow.