Question 326136
{{{ P(B)=1/3=B/12 }}}
{{{ B=4}}}
4 blue marbles
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{{{ P(B or R)=P(B)+P(R)=1/2}}}
{{{1/3+P(R)=1/2}}}
{{{2/6+P(R)=3/6}}}
{{{P(R)=1/6}}}
{{{R/12=1/6}}}
{{{R=2}}}
2 red marbles