Question 983456
Hi Caro!
1.since A and B are independent event,there individual probabilities must be added.
Hence,
  p(A or B)=p(A)+p(B)
 From your question,
 p(A)=0.2
 p(B)=0.5            
Therefore,
   p(A or B)=0.2+0.5
              =0.7
2.your second qestion involves conditional probability which states that,
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{{{p(A/B)=p(A*B)/(p(B))}}}
 if p(A/B)=3/4,
   {{{p(A*B)=1/2}}}
{{{p(B)=(1/2)/(3/4)}}}
{{{p(B)=(1/2)*(4/3)}}}
{{{p(B)=4/6}}}
HOPE THIS HELPS;
------TIMNEWMAN------