Question 209308
The  basic  principal  is  distribution,  which  is  like  compensation  math.
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Remember, 2 * 49 = 2*(50-1) = 100-2 =98,,,,,the  2  is  distributed  over  the 50  and  the  1.
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In  this  case,,,6x -2(x-y),,,,,the  (-2)  is  distributed over  the  (x),  and  the  (-y)
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6x -2(x) -2(-y) 
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6x -2x +2y
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4x +2y
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Note,  somewhere in  the  example a  (-) got  changed
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checking,  let  x=2,,y=3,,in  both  original  and  answer, 14  is  total