a.What is the probability that the three socks selected do not contain a
matching pair?
That means she got one of each color.
She could have selected the red one any of 4 ways, the blue one any of 5 
ways, and the white one any of 5 ways.  That's 4*5*5 = 100 ways.
That's the numerator of the probability.
The denominator is 14C3 = 364.  So the probability that she did not get
a matching pair is  or about 27.5% of the time.  
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 or about 27.5% of the time.  
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b.What is the probability of getting a matching pair among the three drawn
socks?
1 - the probability of getting one of each color =  or about 72.5% of the time. 
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or about 72.5% of the time. 
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c.Suppose four socks are taken from the drawer, What is the probability of not
getting a matching pair?
That's a trick question.  The answer is 0, because there are only 3 colors and
it is therefore impossible to get 4 different colors.  :)
Edwin