I don't know if you are solving with Symbolic Math Toolbox™ or Optimization Toolbox™.
If you have numeric equations (not symbolic), then you should probably use either backslash or, for one variable, an explicit solution. fsolve is for solving systems of nonlinear equations. Or, if you like, you can use fzero, but usng a nonlinear solver to solve a linear equation seems inefficient.
If you have symbolic variables (not numeric) then I am not sure of the best advice.
MATLAB mathematical toolbox documentation