De Morgan's laws let you turn a complement of a union into an intersection of complements, and vice versa:

$$(A \cup B)^c = A^c \cap B^c \qquad (A \cap B)^c = A^c \cup B^c$$

Return a dict with both complements:

key	value
"not_a_or_b"	$(A \cup B)^c$
"not_a_and_b"	$(A \cap B)^c$

Compute each one using the right-hand side of the matching law (complement each event first, then combine) and confirm for yourself that it agrees with the direct route.

solve({2,4,6}, {4,5,6}, {1,2,3,4,5,6})
->  {"not_a_or_b": {1, 3}, "not_a_and_b": {1, 2, 3, 5}}