The list of pregnancy terms for particular species of mammal are nearly normally distributed about a mean pregnancy length with a standard deviation of 16 days. about what percentage of births would be expected to occur within 32 days of the mean pregnancy length?

Whatever the mean pregnancy length is, the standard deviation is 16. So it is WITHIN 32 days meaning that it could be one standard deviation of 16 back from the mean or one above the mean. And according to the empirical rule or something called like that, the percentage of one standard deviations form the mean is 68% theoretically. So 68% is your answer.