I do not have an answer for that, but you should try looking for that on google or yahoo answers.
Answer:
The standard error of the mean is 4.5.
Step-by-step explanation:
As we don't know the standard deviation of the population, we can estimate the standard error of the mean from the standard deviation of the sample as:

The sample is [30mins, 40 mins, 60 mins, 80 mins, 20 mins, 85 mins]. The size of the sample is n=6.
The mean of the sample is:

The standard deviation of the sample is calculated as:

Then, we can calculate the standard error of the mean as:

Answer:
Triangles A & C are right triangles.
Step-by-step explanation:
Triangles A & C are right triangles because they make a 90 degree angle were a pair of legs intersect. That box in the corner of each triangle indicates that the triangle is 90 degrees, therefore a right triangle.
The answer is b your just subtract all the ya lol