The ratio of the number of postcards john had to the number of postcards Zachary ha d was 4:9. Zachary had 45 more postcards than John. After giving some postcards to John, Zachary had 6/7 as many postcards as John.

1 answer

1. A. John has X cards.
   Zack has (X+45) cards.
   
   X/(X+45) = 4/9,
   Cross multiply:
   4x+180 = 9x,
   4x-9x = -180,
   -5x = -180,
   X = 36cards.
   X+45 = 36+45 = 81 cards.
   
   B. Zack has (81-X) cards.
   John has (36+X) cards.
   
   81-X = 6/7(36+X),
   Multiply both sides by 7:
   567-7X = 6(36+X),
   567-7X = 216+6X,
   -7X-6X = 216-567,
   -13X = -351,
   X = 27 cards given to John.

   Answer ID
   528362

   Created
   April 10, 2011 2:17am UTC

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   URL
   https://questions.llc/answers/528362