Given
There are 5 blue marbles, 2 red marbles, and 3 green marbles in a bag
[tex]\begin{gathered} \text{Total Marbles =5+2+3} \\ \text{Total Marbles =10} \end{gathered}[/tex]Probability of selecting a red marble
[tex]\text{Probability of selecting a red marble =}\frac{2}{10}=\frac{1}{5}[/tex]The final answer
The probability of selecting a red marble
[tex]\frac{1}{5}[/tex]