1. Let's start by stating the problem: Introduction to set theory, subsets, and set operations. 2. Set theory studies collections of objects called sets. A subset is a set where every element is also in another set. 3. Important rules: - If $A$ is a subset of $B$, we write $A \subseteq B$. - Set operations include union ($A \cup B$), intersection ($A \cap B$), and difference ($A - B$). 4. Example: Let $A = \{1,2,3\}$ and $B = \{2,3,4,5\}$. - Union: $A \cup B = \{1,2,3,4,5\}$ - Intersection: $A \cap B = \{2,3\}$ - Difference: $A - B = \{1\}$ 5. Explanation: Union combines all elements from both sets without duplicates. Intersection finds common elements. Difference finds elements in $A$ not in $B$. This is the basic introduction to sets, subsets, and operations.