text: You can't solve for X, because that's an expression, not an equation.  You have to have an equal sign in there somewhere to get a value for X.\n\nBTW, no offense to highfive90, but his answer is totally wrong.  x=-10 would make the denominator 0, which is a very bad thing.  If you intended the equation to be 10x/(10+x) = 0, the only solution is x=0.