Respuesta :

first you put them in order least to greatest. 

3,6,6,7,10,11,12,15

then find the median: which in this case is 8.5 (this is the middle of your box plot.

now the lower half of the box is the set (3,6,6,7) find the median of this which is 6 (your box plot starts here)

now to find the end is the set (10,11,12,15) find the median of this which is 11.5 (this is the end of the box)  
You would put 6 at the end , the farthest left