Solving a system of nonlinear equations

Hi all,

I have an algorithm that outputs 5 nonlinear equations with
x,y and z as unknowns. e.g. aX+bY+cZ=W
These are represented in a matrix as:
P= [a b c] and R=[W] (these values are available)

I'm wondering, aside of doing P\R, what other functions
or effective algorithms are good to be implemented in Matlab?
Please don't suggest fsolve as the optimization toolbox is
not supported.

Thank you