Very difficult to help, as difficult to guess what your question means.
This is probably wrong, but are you are asking what is x, if
(b * f)/(e * 2) = x : e and b = 3 ???
If so,
(3f/2)/e = x /e
so x = 3f/2
If, as I suspect, this is not what the question is about,
please read it again carefully
and repost without missing any details.
Regards - Ian
