Answer:

Step-by-step explanation:
Let A and B events. We have defined the probabilities for some events:

Where A' represent the complement for the event A
The complement rule is a theorem that provides a connection between the probability of an event and the probability of the complement of the event. Lat A the event of interest and A' the complement. The rule is defined by:
So for this case we can solve for P(A) like this:

And now we can find
using the total probability rul given by:

And if we replace the values given we got:

And that would be the final answer.
Answer:
x + 3
Step-by-step explanation:
Because he bought an unknown number of soccer balls that is where we use the variable, x. And we know that he bought 3 baseballs, and we add them both to get the total number of things bought. Hope this helped and you could give brainliest :)
I think maybe 3) would make the most sense because she wants a random sample of students and the other options are specific on the type of students.