To find out how many puzzles one student would complete, you can divide the total number of puzzles by the total number of students.
Total puzzles completed = 80
Total students = 15
So, the number of puzzles completed by one student would be:
\[ \text{Puzzles per student} = \frac{80}{15} \approx 5.3333... \]
Rounding this to the nearest tenth gives us:
\[ 5.3 \]
Therefore, the answer is 5.3.