Question 1016090: sam bought two books.one book cost 4.00$ more than three times other.together,the two books cost him 72$ Answer by macston(5194) (Show Source):
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X=cost of book 1; Y=cost of book 2=3X+$4.00
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X+Y=$72 . Substitute (3X+$4) for Y.
X+(3X+$4)=$72
4X=$68
X=$17
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ANSWER 1: Book 1 cost $17.
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Y=3X+$4=3($17)+$4=$51+$4=$55
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ANSWER 2: Book 2 cost $55.
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CHECK:
X+Y=$72
$17+$55=$72
$72=$72
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