Answer:
Mean
Step-by-step explanation:
Given

Required
Best measure of center
The mean is considered the best measure of center when there are no outliers in the given data.
Outlier is when a particular data set is far away from other datasets.
For instance: 20 is an outlier in the following data sets: 
Also, the given data are not open-ended.
An open-ended data is as follows: 
Since we do not have any of the above conditions, then the mean is the best center to use.
Let n be unknown number, then 1/5 of this number is 1/5n. When you add these two numbers, you get

You know that this sum is equal to 24, so

1. Multiply this equation by 5:

2. Solve it:

Answer: n=20, correct choice is B.
A tenth of 24.99 would be the first 9 after the point. In order to round it to the nearest tenth, we must look at the number after it. If that number is 5 or above, we must make the tenth one higher. In this case, the number after the tenth is above 5, so we change the tenth to a 1! Now the number becomes 25.00
If you don’t know we don’t either but ishebrhd