FORMULATION

GAMS
1

Hi
How about this:

alias(i,j);
equations
     eq1(i,k)
     eq2(i,k);
     
 eq1(i,k)..
    sum(j, x(i,j,k)) =E= sum(j, x(j,i,k));
 eq2(i,k)..
    sum(j, x(i,j,k)) =E= y(i,k);

Cheers
Renger