To solve this, let’s first clarify the information given and understand what is required:

1. The Universal Set $U$: Not explicitly provided in the image you shared. Please confirm or provide the universal set $U$ if it has been defined.

2. Sets $A$ and $B$:

   • $A = \{a, b, c, d\}$
   • $B = \{c, d, e, f\}$

Find $A \cap B$ and $A \cup B$:

Step 1: Intersection $A \cap B$

The intersection of $A$ and $B$ includes elements that are in both sets.

Since $A = \{a, b, c, d\}$ and $B = \{c, d, e, f\}$, the common elements are: $A \cap B = \{c, d\}$

Step 2: Union $A \cup B$

The union of $A$ and $B$ includes all elements that are in either $A$ or $B$, without duplication.

$A \cup B = \{a, b, c, d, e, f\}$

Final Answers:

1. Elements in $A \cap B$: $c, d$
2. Elements in $A \cup B$: $a, b, c, d, e, f$

Would you like any further details or explanations?

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1. How do you find the difference between two sets, such as $A - B$?
2. How can you verify if one set is a subset of another?
3. What would $B - A$ look like with these sets?
4. How would you describe the complement of a set in general terms?
5. Why is the universal set important in set operations?

Tip: Always list out each element carefully in unions and intersections to avoid duplication in unions and missing elements in intersections.