Why does this happen?

Toyland is having a sale. all items are 20% off. how much will you save on an item that usually sells for 95$ explain your

Describe in detail how you would construct a 95% confidence interval for a set of 30 data points whose mean is 20 and population standard deviation is 3. be sure to show that you know the formula and how to plug into it. also, clearly state the margin of error.

Which expression gives you the distance between the points (5,1)and(9,-6)