There is a relationship between confidence interval and standard deviation:

Where

is the mean,

is standard deviation, and n is number of data points.
Every confidence interval has associated z value. This can be found online.
We need to find the standard deviation first:

When we do all the calculations we find that:

Now we can find confidence intervals:

We can see that as confidence interval increases so does the error margin. Z values accociated with each confidence intreval also get bigger as confidence interval increases.
Here is the link to the spreadsheet with standard deviation calculation:
https://docs.google.com/spreadsheets/d/1pnsJIrM_lmQKAGRJvduiHzjg9mYvLgpsCqCoGYvR5Us/edit?usp=sharing
Answer:
D
Step-by-step explanation:
The domain is the x value which in this case would be the hours of training
I maybe wrong, but I think it is 14
Simplify both sides of the equation
(Do distributive property)
Add 6v to both sides
Subtract 67 from both sides
Divide both sides by -1
Check the picture below
if your calculator is in Degree mode, you'll get the angle in degrees, if in Radian mode, you'll get radians get taking the inverse sine, so you know