Please help me and I am stuck on this question

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.

Plot the points (0,6), (3,15.8), and (9.5,0) using the graphing tool, and find the function

What are the exclude value of mn+3m