1. The problem statement, all variables and given/known data Let X be a set with exact three elements. Then its power algebra P(x), is an Abelian group with symmetrical difference operator delta. A subset H of P(x) is a subgroup if, for all A, B in H, A deltaB in H. Find all possible subgroups of P(x). 3. The attempt at a solution I have no clue how to begin solving this problem. But I know that the power set of any set X becomes an Abelian group if we use the symmetric difference as operation. How can I show this?