Answer: 0.2
Step-by-step explanation:
Given : The number of blue marbles =3
The total number of marbles = [tex]3+7+5=15[/tex]
Now, If Joe picks 1 marble from the bag at random, then the probability that it will be blue :-
[tex]\text{P(Blue)}=\dfrac{\text{Number of blue marbles}}{\text{Total marbles}}\\\\\=\dfrac{3}{15}=\dfrac{1}{5}=0.2[/tex]
Hence, the probability that it will be blue = 0.2