1. **State the problem:** We are given two sets $P = \{a, b, c, d, e\}$ and $R = \{t, d, c, b, e\}$. We need to find the set difference $P - R$. 2. **Formula and explanation:** The set difference $P - R$ is defined as the set of elements that are in $P$ but not in $R$. Mathematically, $$P - R = \{x \mid x \in P \text{ and } x \notin R\}.$$ This means we remove all elements from $P$ that also appear in $R$. 3. **Identify common elements:** Elements in $P$ are $a, b, c, d, e$. Elements in $R$ are $t, d, c, b, e$. The common elements are $b, c, d, e$. 4. **Remove common elements from $P$:** Removing $b, c, d, e$ from $P$ leaves only $a$. 5. **Final answer:** $$P - R = \{a\}.$$