Question 859160
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Hi,
Let x represent the son's time
 1/4 + 1/x = 1/1           |Multiplying thru by 4x so as all denominators = 1
  x + 4 = 4x    
      4/3 = x, the son's time, 1 <sup>1</sup>&frasl;<sub>3</sub> hr 0r 1 hr 20min