Array indexing future values multiple variables

x1(i+1)=x1(i)+x2(i); x3(i+1)=x3(i)+x4(i); x5(i+1)=x5(i)+x6(i);

x2(i+1)=x2(i)-1/(m0+m1+m2)*((1/2*m1*l1+m2*l1)*cos(x3(i))*x4(i+1)-(1/2*m2*l2*cos(x5(i)))*x6(i+1)-sigma0*x2(i)+(1/2*m1*l1+m2*l1)*x4(i)*sin(x3(i))*x4(i)-1/2*m2*l2*cos(x5(i))*x6(i)-F);

x4(i+1)=x4(i)-1/(J1+m2*l1^2)*((1/2*m1*l1+m2*l1)*cos(x3(i))*x2(i+1)-(1/2*m2*l1*l2*cos(x3(i)-x5(i)))*x6(i+1)-1/2*m1*l1*cos(x3(i))*x2(i)-(sigma1+sigma2)*x4(i)-(-sigma2-1/2*m2*l1*l2*x6(i)*sin(x3(i)-x5(i)))*x6(i)+(1/2*m1+m2)*g*l1*sin(x3(i)));

x6(i+1)=x6(i)-1/J2*(1/2*m2*l2*cos(x5(i))*x2(i+1)-1/2*m2*l1*l2*cos(x3(i)-x5(i))*x4(i+1)-1/2*m2*l2*cos(x5(i))*x2(i)-(-sigma2-1/2*m2*l1*l2*x6(i)*sin(x3(i)-x5(i)))*x4(i)-sigma2*x6(i)-1/2*m2*g*l2*sin(x5(i)));

In this system of equations, x2(i+1) depends on x4(i+1) and x6(i+1), x4(i+1) depends on x2(i+1) and x6(i+1), x6(i+1) depends on x2(i+1) and x4(i+1).How can I find x1,x2,x3,x4,x5 and x6?