Answer:
0.8213
Step-by-step explanation:
-This is a binomial probability problem given by the function:

Given that n=21 and p=0.2, the probability that she experience a delay on at least 3 days is calculated as:

Hence, the probability that she experience delay on at least 3 days is 0.8213
I think you forgot to give the options along with the question. I am answering the question based on my research and knowledge. "Some customers who rate their service as high quality return for additional services" is the conclusion that can be drawn from this study. I hope that the answer has actually come to your desired help.
10 / (2/5)...when dividing with fractions, flip what u r dividing by, then multiply
10 * 5/2 = 50/2 = 25...so there are 25 of them