let x is the random variable that represents the speed of car.
[tex]\begin{gathered} \mu(\operatorname{mean})=90 \\ \sigma=10 \end{gathered}[/tex]
probability that x is higher than 100 :
[tex]P(x>100)[/tex]
for x=100:
[tex]\begin{gathered} z=\frac{x-\mu}{\sigma} \\ z=\frac{100-90}{10} \\ z=1 \end{gathered}[/tex]
so,
[tex]p(x>100)=p(z=1)[/tex]
probability =total area - area of the left of (z=1)
[tex]\begin{gathered} \text{probability}=1-0.8413 \\ p(x>100)=0.1587 \end{gathered}[/tex]
and the area of the left of z=1 is 0.8413 (from normal distribution)
