How to use Genetic Algorithm ?

I have a system of equations as given following:

z=[3 7 10 27 30 42]; p=[10.2 8.7 7.1 6.4 3.2 2];

PROBLEM: ((x1*x2)+x2-(x3*x4)+z)/((x1-x2)*z+(x3*x4))=p;

As I have 4 unknowns(x1,x2,x3,x4), z and p is a vectors So I need at least 4 equations to solve this problem. I have length(z)=length(p)=6, It means I have 6 equation and 4 unknown to solve.

How can I use genetic algorithm to solve this problem. As I saw in MATLAB help command is given like that: [x,fval,exitflag,output] = ga(fitnessfcn,nvars,A,b,Aeq,beq,LB,UB,nonlcon,options),

How should use this to solve my problem. Thanks in Advance