Question: What is the mode of the values $5.6$, $8.7$, $8.7$, $3.1$, $5.6$, $8.7$?
1. The problem asks for the mode of the data set: $5.6$, $8.7$, $8.7$, $3.1$, $5.6$, $8.7$.
2. The mode is the value that appears most frequently in a data set.
3. Count the frequency of each value:
- $5.6$ appears 2 times.
- $8.7$ appears 3 times.
- $3.1$ appears 1 time.
4. Since $8.7$ appears the most times (3 times), the mode is $8.7$.
**Final answer:** $8.7$