Question 685145
formula:
z = (x-μ)/σ
.
a. μ = 80 and σ = 10
z = (x-μ)/σ
z = (100-80)/10
z = 20/10
z = +2
.
b. μ = 80 and σ = 5
z = (x-μ)/σ
z = (100-80)/5
z = 20/5
z = +4
.
c. μ = 105 and σ = 10
z = (x-μ)/σ
z = (100-105)/10
z = -5/10
z = -0.5
.
d. μ = 105 and σ = 5 
z = (x-μ)/σ
z = (100-105)/5
z = -5/5
z = -1