another thing.... does 'x' in the eq'n signify multiplication? or is it a variable? you have to understand what kylekatarn is trying to say in his post: it is virtually impossible to solve one eq'n in 5 unknowns! you have to tell us which is known, and which is unknown (like wcy said, we have to know whether or not that 'e' you've used is the natural exponential!); i.e., do we solve for a? or some other variable?
I'm getting to think this isn't a serious topic... just like kylekatarn said! especially since you didn't simplify the (8+18-20) part of it before you posted....