Answer:
115.3 hertz
Step-by-step explanation:
For either interval, the value of the sample mean is given by the average of the lower and upper bound of the confidence interval. Since both intervals were constructed by using the same sample, both values should be equal.
For the first interval:

For the second interval:

Answer:
c = 4
Step-by-step explanation:
Simplifying
3c + 6 = 18
Reorder the terms:
6 + 3c = 18
Solving
6 + 3c = 18
Solving for variable 'c'.
Move all terms containing c to the left, all other terms to the right.
Add '-6' to each side of the equation.
6 + -6 + 3c = 18 + -6
Combine like terms: 6 + -6 = 0
0 + 3c = 18 + -6
3c = 18 + -6
Combine like terms: 18 + -6 = 12
3c = 12
Divide each side by '3'.
c = 4
Simplifying
c = 4