I’m not sure but since no one else commented I would think it’s D, I think you take the first number like 6 for a and subtract the first number for b like 3
X = 97
Working on other question.
Vertical angles are congruent, so
107=3x-4
3x=111
x=111/3=37°
Answer:
center = 98.6, variability = 0.08
Step-by-step explanation:
The Central Limit Theorem estabilishes that, for a random variable X, with mean
and standard deviation
, the sample means with size n of at least 30 can be approximated to a normal distribution with mean
and standard deviation 
The center is the mean.
So 
The standard deviation of the sample of 50 adults is the variability, so

So the correct answer is:
center = 98.6, variability = 0.08