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Hi
Population: μ=100 and standard deviation σ=20.
 P (A < x < B) = P (z1 < z < z2) = P (z < z2) - P (z < z1)
 P (95 < x < 110) = 
P (-5/20 < z < 10/20) = P (x < .5) - P (z < .25) = .6815-.5987 = .0828
Below: find z-scores:  P (95 < x < 110) is the area under normal curve between z-values
For the normal distribution: Below:  z = 0, z = ± 1, z= ±2 , z= ±3 are plotted.  
Area under the standard normal curve to the left of the particular z is P(z)
Note: z = 0 (x value: the mean) 50% of the area under the curve is to the left and 50%  to the right
