Answer:
The median increases to 7
Explanation:
List the numbers in chronological order,
5, 5.5, 6, 6.5, 6.5, 7, 7.5, 8, 8, 8.5
As of now, the median is 6.75.
When a shoe size of 9 is added, we have
5, 5.5, 6, 6.5, 6.5, 7, 7.5, 8, 8, 8.5, 9
Now, the median is 7.