Answer:
0.173 probability that she gets exactly three questions correct.
Step-by-step explanation:
For each question, there are only two possible outcomes. Either she guesses the correct answer, or she does not. The probability of guessing the correct answer for a question is independent of other questions. So we use the binomial probability distribution to solve this question.
Binomial probability distribution
The binomial probability is the probability of exactly x successes on n repeated trials, and X can only have two outcomes.

In which
is the number of different combinations of x objects from a set of n elements, given by the following formula.

And p is the probability of X happening.
Seven questions:
This means that 
Each question has four choices.
Abby guesses, which means that 
Find the probability to the nearest thousandth, that Abby gets exactly three questions correct.
This is P(X = 3).


9/3x = 5/8
Using the reciprocal, multiply each side by 3/9.
5/8 * 3/9 = 15/72
Simplify it : 5/24
x = 5/24
Hope this helps :)
Answer:
50 students per bus and 9 students per van
Step-by-step explanation:
I just guessed until I got it right, so I don't really have a method. If I ever find a better way of doing it, I'll edit my answer.
12/6 + 2/3 + 3/4
MMC of 6, 3 and 4 is 12
So 24+8+9/12 = 41/12 = 3,41 approximately.