I have a group of 20 students who took the first exam, and the mean and standard deviation of their grades was 28(±9.15)
They took the second exam. The mean and standard deviation of their grades in the second exam is unknown, but it is less than the first exam by 14(±9.9)
My question is: How to find the mean of their grades AND the standard deviation in the second exam if I am given these numbers only?