My question is in the image as well as the problem.

We have 6 faces
the number that we want to obtain is 3 and 6 because they are multiples of 3
the probability for one face is 1/6
The probability for the multiples of 3 is
[tex]P=\frac{1+1}{6}=\frac{2}{6}=\frac{1}{3}[/tex]the probability is 1/3 = 1 out of 3