Answer:
Step-by-step explanation:
a. I think it's "7 or 1,5,7"
when we use "or" it means the union of two sets
P(A U B)=P(A)+P(B)
= [tex]\frac{1}{15} + \frac{3}{15} = \frac{4}{15}[/tex]
b. I think it's "5 or a number divisible by 3 or 7"
P(A U B)=P(A)+P(B)
there are 5 numbers divisible by 3 from 1-15, and 2 are divisible by 7 from 1-15, so
[tex]\frac{1}{15} +\frac{5}{15} +\frac{2}{15} = \frac{8}{15}[/tex],
I am not sure if it is really "divisible by 3 or 7" or "divisible by 3 and 7", the correctness of my answer varies with how you wrote your question.