What is the median of the following numbers: 3, 5, 8, 12, 15?

To determine the median of a set of numbers, you first need to arrange the numbers in ascending order, which in this case are already sorted as: 3, 5, 8, 12, 15. The median is the middle number in a list when the numbers are organized from least to greatest.

When the list has an odd quantity of numbers, as it does here with five values, the median is simply located at the center. To find the middle number in this scenario, you can count towards the center of the list. The first number is 3, the second is 5, the third is 8, the fourth is 12, and the fifth is 15. The third number here is 8.

Hence, the median of the given set of numbers is 8, which makes it the correct choice.