Question 644513
If x ∉ S ∩ T, then x is NOT in both sets at the same time. So it must be in one or the other set (or in neither set). So x is exclusively in one set, but not in the other.


So say x is in set T, but not in set S. Then X ∉ S would be true.


OR


say x is in set S, but not in set T. Then X ∉ T would be true.


If x is in neither set, then both X ∉ S and X ∉ T would be true.