Question 1114092
b) It must either rain or not rain so,
{{{P[NR]+0.42=1}}}
{{{P[NR]=1-0.42}}}
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c) Probability must a number between 0 and 1.
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d) Find the probability that the ball is yellow. 
{{{P(Y)=8/(5+7+8)=8/20=2/5}}}
So the complement would be the probability of not yellow.
{{{P(NY)=1-2/5}}}
{{{P(NY)=3/5}}}
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e) {{{P(B)=1/2}}}
Let the number of blue balls added be equal to X,
{{{(5+X)/(20+X)=1/2}}}
{{{2(5+X)=1(20+X)}}}
{{{10+2X=20+X}}}
{{{X=20-10}}}