To plot the box and whisker for the given set of data we need to rearrange the data in ascending order and determine, the lowest value, the lower quartile, the median, the upper quartile and the highest value.
30,27,32,25,12,22,20,29,35,35,28
rearranging it gives us:
12,20,22,25, 27,28,29,30,32,35,35
lowest value is 12
highest value is 35
median=28
lower quartile 23.5
Upper quartile 31
thus the boxplot will be: