Find the Standard Deviation

A radar unit is used to measure the speed of automobiles on the expressway during rush hour traffic. The speeds of the car are normally distributed with a mean of 62 miles per hour. If nine percent of the cars exceed the speed limit of 65 miles per hour, find the standard deviation of all the speeds.

So far I have figured out this:

50% are going less than 62 mph

41% are 62 mph to 65 mph

9% are going over 65 mph

Where would I go from there?

Can you find the number x such that standard z-score is
\(\displaystyle P(Z > x) > .09\;{\rm{or}}\;P(Z \le x) = .91\)?

Then you need to solve this \(\displaystyle \frac{{66 - 62}}{\sigma } = x\).