I'm confused by this problem. The average price for a gallon of gasoline in the United States is $3.73 and in Russia it

is $3.40 (Bloomberg Businessweek, March 5-March 11, 2012). Assume these averages

are the population means in the two countries and that the probability distributions are

normally distributed with a standard deviation of $.25 in the United States and a standard

deviation of $.20 in Russia. c. what is the probability that a randomly selected gas station in Russia charged more

than the mean price in the United States?

How do I get from Z=3.73-3.40/.20

=1.65

to

P(z>1.65)=1-P(z1.65)

=1-0.9505

=0.495

I'm confused by the methodology.