weekly wages at a certain factory are normally distributed with a mean of $400 and a standard deviation of $50. find the probability that a worker selected at random makes $500 and $550.

So you must be working with the standard bell curve. If the mean is 400, and ONE standard deviation is 50, 500 would be 2 standard deviations from the mean, and 550 would be 3 standard deviations from the mean. The probability would be 2.35% -see picture