by normal curve symmetry
from normal table
we have z = 1.15 , z = -1.15
z = (x - mean) / sigma
1.15 = (x - 150) / 25
x = 178.75
z = (x - mean) / sigma
-1.15 = (x - 150) / 25
x = 121.25
interval is (121.25 , 178.75)
Pr((121.25-150)/25 < x < (178.75-150)/25)
is about 75%
