28. multiply 12 by 5 =-60
29. divide 39 by 3 = 13
30.divide 15 by 4 = 3.75
31. multiply 2 by 10 = -20
Option D. 2(n + 9) is the right answer
Step-by-step explanation:
The word problems are converted into mathematical problems to solve simply.
for the given problem
"two times the sum of a number and 9"
Let n be a number then
when there is and between two things they are performed first then next operation is performed so
the sum of a number and 9

Then
two times the sum of a number and 9

Hence,
Option D. 2(n + 9) is the right answer
Keywords: Mathematical notation
Learn more about mathematical notation at:
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Using the <u>normal distribution and the central limit theorem</u>, it is found that there is a 0.1635 = 16.35% probability of a sample result with 68% or fewer returns prior to the third day.
In a normal distribution with mean
and standard deviation
, the z-score of a measure X is given by:

- It measures how many standard deviations the measure is from the mean.
- After finding the z-score, we look at the z-score table and find the p-value associated with this z-score, which is the percentile of X.
- By the Central Limit Theorem, for a proportion p in a sample of size n, the sampling distribution of sample proportions has mean
and standard error 
In this problem:
- Sample of 500 customers, hence
.
- Amazon believes that the proportion is of 70%, hence

The <u>mean and the standard error</u> are given by:


The probability is the <u>p-value of Z when X = 0.68</u>, hence:

By the Central Limit Theorem



has a p-value of 0.1635.
0.1635 = 16.35% probability of a sample result with 68% or fewer returns prior to the third day.
A similar problem is given at brainly.com/question/25735688
Answer:
189,2$
Step-by-step explanation:
220*0,86=189,2
14% = 14/100 = 0,14
1-0,14 = 0,86
price* factor between 0 and 1, 0 -> item is free, 1 -> full price
Let's use x as the number of questions she answered correctly. If we make an equation of out the question, it would be 8.7x+13=108.7 To solve the equation subtract 13 from both sides. So it will leave you with 8.7x=108.7-13, which is 8.7x=95.7. Divide both sides by 8.7, which will give you x=11. She answered 11 questions correctly.