I'm not sure what KO means, so I'll diregard that for now.
How do we figure out the range of a data set?
The rules state we must find the difference between the smallest and largest numbers in the data set.
Let's organize the numbers, least to greatest.
[tex](3, 5, 7, 8, 12, 12, 15)[/tex]
Because we organized this from least to greatest, all we need to do is subtract the first number from the last number:
[tex]15 - 3 = 12[/tex]
That means...
The range of the data set is 12!
Please let me know if this helped you, or if you have any questions!