Question 253080
Use a z-table.  One is located at: http://www.easyhomeworkhelp.com/statistics/ztable.jpg
+1 standard deviation is the same as a z-score of 1.0.  From the table, it has a z-score = .8413.  Therefore, 84.13% of plumbers make less than $3300, and 1-.8413=.1587, or 15.87% of plumbers make more than $3300.
Hope this helps! :-)