If I have the formula [see details] how do I make wolframalpha.com solve for X?

You would use the solve function, like this:

solve Y=X+A+B+(X+A) C/100+(X+A+B) D/100+(X+A+B) E/100+(X+A+B) F/100 for X

However, Alpha seems to have a limit on the length of the equations you can solve or possibly the number of variables it can compute.

I get X=-(B (100+D+E+F)+A (100+C+D+E+F)-100 Y)/(100+C+D+E+F) from Mathematica so there’s no problem with the solve function in Alpha (which is the same as in Mathematica). It probably just limits the amount of computation available for each user.

Removed by Fluther moderators.

@Shuttle128: Thank you. I first purchased version 2 of Mathematica back in the early 90’s. Naturally I was very excited when I heard about wolframalpha.com. I found several uses for wolframalpha.com but each time there was a problem. Unfortunately Wolfram seems determined to make sure that no one actually uses their service. Hopefully Google will integrate symbolic algebra into google.com just as they have unit conversions and basic arithmetic. Google’s services are actually usable.

PS: I see that 4/5ths of the comments were moderated. What happened?

LOL…I just modded mine for fun…See, if the Great answer and Flag as links are still there, it wasn’t really modded!

My first one got modded, but I can’t for the life of me remember what i said to incur the wrath of the mods!

Just playing @malevolentbutticklish