Answer:
The man firstly crosses the river with the chicken. (the fox and corn are safe together).
The man then returns and takes the fox across the river, and brings the chicken back since he can't leave the fox and chicken together.
Again, since the chicken and corn can't be left together, he leaves the chicken and he takes the corn across and leaves it with the fox.
He then returns to pick up the chicken and heads across the river one last time.
