Answer:

Step-by-step explanation:
By definition if two events are mutually exclusive then they are disjoint events, that is, they can not occur at the same time.
In general terms we say that events are mutually exclusive, then:

In this case we have that

But A and B are mutually exclusive events, then 
Answer:
35 students
Step-by-step explanation:
So if every 3 boys there is 4 girls you can solve that there is 5 times the amount of girls to get to 20. So to solve for the boys you do the same.
3 x 5 = 15
That means there are 15 boys and 20 girls but we want to know the total so what you do is just add 15+20=35
So 35 total students.
Hope that helps and have a great day!
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