The ages of trees in a forest are normally distributed with a mean of 25 years and a standard deviation of 5 years.

Complete question is in comment section :

68%

Step-by-step explanation:

Mean = 25

Standard deviation = 5

The percentage of trees between 20 and 30

20 trees = 1 standard deviation below the mean ; mean - 1(standard deviation)

25 - 5 = 20

30 trees = 1 standard deviation above the mean ;

Mean + 1(standard deviation) ;

25 + 5 = 30

This means, 20 and 30 lies ±1 standard deviation from the mean which according to the empirical rule is 68%

According to the empirical rule :

a line is an defined derm because it

a)contains an infinite number of points b) can be used to create other geometric shapes c)describes something that does not have width or depth d) is a term that does not have a formal definition. a line is an undefined term because it: contains an infinite number of points.