9.88,10.19,11.15,11.70,12.01,12.46, 13.22,13.29,14.00,14.38,14.50,14.50 ,15.14,15.16,15.16,15.16,15.54,15.9 6,16.20,16.22,16.44,17.58,20.38,21. 15 is the data set, how do i find the quartiles?

You can use this website called Quartiles Calculator to help you with this question. By the way the websites when you search it up it will be the first link that pops up. :) 
But don't type the question, just the type or copy and paste the numbers of your question as it will say. 

Apples are more expensive by 11/3