Solution
(a) red marble?
[tex]p=\frac{\text{red}}{\text{total}}=\frac{3}{3+13+4+8}=\frac{3}{28}[/tex](b) green marble?
[tex]p=\frac{\text{gren}}{\text{total}}=\frac{13}{3+13+4+8}=\frac{13}{28}[/tex](c) blue marble?
[tex]p=\frac{\text{blue}}{\text{total}}=\frac{4}{3+13+4+8}=\frac{4}{28}[/tex]