Question 772066
Hi,

For this problem, you will need to find the MEAN and STANDARD DEVIATION from the data.

After you found both, you will able to solve part (a) to part (c):

a) z = (81 - mean)/ s. d = ?

b)  P(X <= 81) = P( z < result of part a) = ?

Note: X is variable

c) P( 60 < x < 75)

You will find 

z(60)  and z(75) the same process in part (a) and part (b)

z(60) = (60 - mean)/ s.d ?

P(z(60) < z < z(75) = ?

z(75) = (75 - mean)/s.d = ?

Hope it helps you!

John10 (john100185@yahoo.com)