The median of the following distribution is: 7, 9, 5, 3, 10, 15, 21, 19, 17 ans. 10 15 9 17

To find the median of a distribution, you need to follow these steps:

1. Arrange the numbers in ascending order: 3, 5, 7, 9, 10, 15, 17, 19, 21
2. Find the middle number. If there is an odd number of observations, the median is the middle number. If there is an even number of observations, the median is the average of the two middle numbers.

In this case, there are 9 numbers, so the median is the 5th number, which is 10. So, the answer is 10.