Tìm y: a) 30 :y +15 :y = 90 b) 25 ×y -10 ×y = 45

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1. a) 30 :y +15 :y = 90

   => (30 +15) :y = 90

   => 45 :y = 90

   => y = 45 :90

   => y = 1/2

    Vậy y = 1/2

   b) 25 ×y -10 ×y = 45

   => (25 -10) ×y = 45

   => 15 ×y = 45

   => y = 3

     Vậy y = 3

    

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2. a)

   30 : y + 15 : y = 90

   (30 + 15) : y = 90

   45 : y = 90

   y = 45 : 90

   y = 0,5

   b)

   25 × y – 10 × y = 45

   (25 – 10) × y = 45

   15 × y = 45

   y = 45 : 15

   y = 3

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