I honestly kinda know what I'm doing but it just doesn't make sense to me

Find the x coordinate of the point.

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.

What is the length of the unknown leg in the right triangle ?