Answer: The number of parallelograms that fall into the category A ∪ B is 26.
Step-by-step explanation: The given diagram shows the universal set U defined by
U = {parallelograms}.
Set A represents parallelograms with congruent sides and set B represents parallelograms with four congruent angles.
We are to find the number of parallelograms that fall into the category A ∪ B.
From the diagram, we find that

From set theory, we have

Thus, the number of parallelograms that fall into the category A ∪ B is 26.