I am having trouble trying to solve this equation.
Batting averages of major league baseball players are thought to possess a mound-shaped symmetric distrution with a mean of .260 and a standard deviation of .03. Find the proportion of major league baseball players who have a batting average that exceeds .230.
If you look here you can see what that "mound shape" looks like
Now, 0.230 is just 1 Standard Deviation from 0.260 (0.230 + 1×0.03 = 0.260), and when you look up the table you find 1 Standard Deviation = 0.3413, this means that 34.13% of the population are between 0.230 and 0.260, now 50% are above the mean of 0.260, so 84.13% (34.13%+50%) are above 0.230.
"The physicists defer only to mathematicians, and the mathematicians defer only to God ..." - Leon M. Lederman