Question 1027435
You could choose either green then red or red then green so calculate both ways and add.
Green first, red second: {{{P(G)=4/(10+5+4+1)=4/20=1/5}}}
{{{P(R)=5/19}}}
{{{P(G,R)=(1/5)(5/19)=1/19}}}
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Red first, green second: {{{P(R)=5/20=1/4}}}
{{{P(G)=4/19}}}
{{{P(G,R)=(1/4)(4/19)=1/19}}}
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So then,
{{{P=1/19+1/19=2/19}}}

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Similarly,

Blue first, yellow second: {{{P(B)=10/20=1/2}}}
{{{P(Y)=1/19}}}
{{{P(B,Y)=(1/2)(1/19)=1/38}}}
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Yellow first, blue second: {{{P(Y)=1/20}}}
{{{P(B)=10/19}}}
{{{P(Y,B)=(1/20)(10/19)=1/38}}}
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So then,
{{{P=1/38+1/38=1/19}}}