ok i just made a post trying to answer the post by jkds but accidentally erased it. I have been studying it though. One thing that always confused me about algebra is that numbers seem to come out of thin air. Example .073 = 1/ (1+.75s)...........so.......13.69 = 1+.75s,......12.69 = .75s........s =16.93. Where is he 13.69 coming from