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
[tex]n(A)=12+8=20,\\\\n(B)=6+8=14,\\\\n(A\cap B)=8,\\\\n(A\cup B)=?[/tex]
From set theory, we have
[tex]n(A\cup B)=n(A)+n(B)-n(A\cap B)=20+14-8=26.[/tex]
Thus, the number of parallelograms that fall into the category A ∪ B is 26.