Respuesta :

IQR is the Q3 - Q1 

Put the data in order.....

6, 7, 11, 13, 14, 15, 15, 19, 21 
       ^             ^             ^  
      9(Q1)     14(Q2)    17(Q3) 

17 (Q3) - 9 (Q1) = 8 (IQR) 

So the answer to your question is the first option, 8. 

Hope this helps! :D