ANSWER
1) 9
2) Not enough information
3)
EXPLANATION
Given;
The number of yellow marbles is 30;
The number of chosen yellow marbles ;
[tex]\begin{gathered} \frac{7}{10}\times30 \\ =7\times3=21\lbrack \end{gathered}[/tex]
The number of yellow marbles which were not chosen;
[tex]30-21=9[/tex]
