Please help me to solve the following questions : 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 .