Im trying to combine this two equations to solve it:

http://www.physicsforums.com/latex_i.../1659673-1.png

and

http://www.physicsforums.com/latex_i.../1659673-2.png

I got this far:

0.5 = ( 0.876 - VAf ) / (VAf + 8.76)

Is it possible to find out what VAf is from this?

James