The Venn diagram shows two sets, $A$ and $B$, with elements distributed across four regions:

• Region I: Elements in set $A$ only = 29
• Region II: Elements in both set $A$ and set $B$ (intersection) = 15
• Region III: Elements in set $B$ only = 6
• Region IV: Elements outside both sets $A$ and $B$ (the universal set but not in $A$ or $B$) = 26

The problem asks how many elements belong to both set $A$ and set $B$. This refers to the number of elements in the intersection of $A$ and $B$, which is located in Region II of the Venn diagram.

Thus, the number of elements in both $A$ and $B$ is: $\boxed{15}$

Would you like more details or have any other questions?

Here are 5 related questions to expand your understanding:

1. How would you find the total number of elements in set $A$?
2. How would you calculate the total number of elements in set $B$?
3. What is the total number of elements in the universal set $U$?
4. How would you find the number of elements that are either in set $A$ or set $B$?
5. What is the difference between the union and intersection of two sets?

Tip: When working with Venn diagrams, remember that the intersection represents elements common to both sets, while the union covers all elements from both sets.