What is it you want to know? You've been told in another thread that expressions of this sort:
are undefined and compiler dependent. In the case of this code, it appears that j is assigned i+i (3+3=6) then i is incremented twice (i++; i++; so i is now 5), but not until after the assignment operation.
There's no reason why any sane programmer would ever need to use such an expression.
Why is this "urgent"?