Question 859767
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Hi,
Let x represent How many days can C finish the job alone 
 {{{1/5 + 1/4 + 1/x = 1/2}}}     |Multiplying thru by 20x so as all denominators = 1
   4x + 5x + 20 = 10x
             20 = x, How many days can C finish the job alone