If $X$ is a normally distributed random variable with standard deviation $\sigma=10$, and $P(X>16.34) = .1212$, what is the mean (expected value) of $X$?
Attempt at solution: This problem doesn't make sense... standard deviation is given, by the probability $X>16.34$ has no upper bound, so how can this be computed? The expected value is just the summation of all the values which $=.1212$ here, so I'm not exactly sure what is being asked. please help!