Answer :
Given that the bag contains three coloured tiles as,
3 Red, 6 Green and 3 Blue.
A tile is randomly selected, total ways are
[tex]\begin{gathered} =^3C_1+^6C_1+^3C_1 \\ =3+6+3 \\ =21 \end{gathered}[/tex]selecting a green will be given as ,
[tex]\begin{gathered} =^6C_1 \\ =6 \end{gathered}[/tex]So, the required probability is given as,
[tex]\begin{gathered} P=\frac{6}{21} \\ =0.2857 \end{gathered}[/tex]