Just because you want to solve a general system of nonlinear equations, does not mean an analytical solution can be shown to exist. In fact, it is essentially trivial to generate an equation that has no such solution for the roots.
If all of the many parameters in your equations have known numerical values, then you can use one of many numerical solvers. If not, then you essentially have no recourse. As I said, just wanting something is not sufficient, even if you need it very badly.
You could do some things, like eliminate some of the linear variables, solving for them in terms of the others. While this is theoretically possible, even that will surely be incredibly computationally complex. But then you will be left with a nonlinear kernel, one that will very possibly have no solution at all. After all, solve did give up. This is difficult to know, but it does suggest you need to reconsider how you are trying to solve this problem.
