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1) There are three box : box X has 10 bulbs which 4 are defective

Box Y has 6 bulbs which 1 are defective

Box Z has 8 bulbs which 3 are defective

a box is chosen at random and the buld is randomly selected from the choosen box . If the bld is not defective, find the probabily that it come from box Z .(Answer = 75/247)

2) A pair of fair dice is thrown . If two numbers are different , find the probability that

a)the sum is 6( answer=2/15)

b)an ace appears (answer=1/3)

c)the sum is 4 or less (answer = 2/15)

d)the sum is even (answer is 2/5)

the sum exceeds nine (answer is 2/15)

3)One couple has two children , find the probability both children are boys if

a)at least one of the children is a boy (answer is 1/3)

b)the older child is a boy (answer is 1/2)

I cannot solve most of the questions above because I don't know how to find the P(A n B) since P(A|B)=P(A n B)/P(B) . So, please help me to solve the questions .Thank you .