Question 975417
z=(x-mean)/sd

z=(12.00-12.80)/2.85;;  This is - 0.80/2.85=-0.28
z=(16.00-12.80)/2.85;; this is  3.20/2.85= 1.12

probability in this range is 0.4789;  

z=(12-15.45)/2.98;;this is -1.16
z=(16-15.45)/2.98;;this is  0.18

probability is 0.4483

The probability is heavily weighted towards the right end for the first and towards the left for the second.  Another way of saying it as that most of the probability is fewer than 12 years for the first group and greater than 16 years for the second.