Answers

2016-03-31T20:11:17+08:00
A 42 years man has  a 12 years old son now
in how many years time will the fatter be twice as old as his son
        let x be the # of years time when the father will be          twice as old as his son
         the equation will be     42 + x  =   2(12 + x)
                                        x =   42-24  =  18 years
  check
             in 18 years time the father age =  42 + 18 = 60
                                               son age   =  12 + 18   =30
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