I believe it would be B but I'm not 100% sure. Like i warn everyone, TRUST SOMEONE ELSE BEFORE TRUSTING ME. I would hate to see you get the wrong answer cause of me...
Best Hopes,
Cupkake~
The answer to your question is:
1/3x + 1/2x = x - 9
Answer: 0.9617
Step-by-step explanation:
Given : The proportion of adults use their phones in meetings or classes : p=0.57
Number of adults randomly selected : n= 9
Let x be the random variable that represents the number of adults use their phones in meetings or classes.
By using binomial probability formula, to find the probability of getting success in x trials.

The probability that at least 3 of them use their smartphones in meetings or classes will be :-

Hence, the required probability is 0.9617 .