Find standard deviation in years

Question

The average age of passenger cars is 19.4 years. If the distribution of ages is normal and 9% of the cars are older than 22.1 years find the standard deviation. Round z-value to 2 decimal places.

Answer 1

The standard deviation = 2.02

Mean = 19.4

z-value for 9% = 1-0.09 = 0.91 which is equal 1.34 from the z-table

X= 22.1

Followed by the z score formula