Question: What is the value of $n(F' \cap G')$?
1. **State the problem:** We are given a Venn diagram with two sets $F$ and $G$ inside a universal set $\xi$. The numbers represent the counts of elements in different regions:
- $12$ in $F$ only
- $3$ in $F \cap G$
- $8$ in $G$ only
- $7$ outside both $F$ and $G$
We need to find $n(F' \cap G')$, the number of elements outside both $F$ and $G$.
2. **Recall the definition:**
- $F'$ is the complement of $F$, meaning elements not in $F$.
- $G'$ is the complement of $G$, meaning elements not in $G$.
- $F' \cap G'$ is the set of elements not in $F$ and not in $G$.
3. **Identify the region:**
From the diagram, the number outside both $F$ and $G$ is given as $7$.
4. **Conclusion:**
Therefore, $n(F' \cap G') = 7$.
This is the count of elements outside both sets $F$ and $G$.