Answer:
[tex]P(B)=\frac{1}{3}[/tex]
Step-by-step explanation:
The number of red marbles in the bag is; [tex]n(R)=3[/tex].
The number of blue marbles in the bag is; [tex]n(B)=4[/tex].
The number of white marbles in the bag is; [tex]n(W)=5[/tex].
The total number of marbles in the bag is: [tex]n(S)=3+4+5=12[/tex].
The probability of selecting a blue marble is [tex]P(B)=\frac{n(B)}{n(S)}[/tex]
We substitute the given information to obtain:
[tex]P(B)=\frac{4}{12}[/tex]
We simplify to obtain:
[tex]P(B)=\frac{1}{3}[/tex]
