You need to standardize the sample mean.
So,
Since the corresponding x value can be solved via .
a) X ~ N(10, 0.25)
Find P( > 10.25) where n = 10
Find x such that P( > x) = 0.05 where n = 10
b) X ~ N(20.2, 4)
Find P( < 19) where n = 20
Find x such that P( < x) = 0.85 where n = 20
If someone could do a) as an example I should be able to do b. Also the are supposed to be capital X's with the hat on top.
Thanks in advance.