Tìm `x` biết `13/28*x=1/7*(555/222+444/12221+33333/244442+11/330+13/60)`.

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1. * Sửa đề : `13/28 . x = 1/7 . ( 555/222 + 4444/12221 + 33333/244442 + 11/330 + 13/60 )` ( Đề gặp rồi nên biết )

   * Bài làm :

   `13/28 . x = 1/7 . ( 555/222 + 4444/12221 + 33333/244442 + 11/330 + 13/60 )` 

   `⇔ 13/28 . x = 1/7 . ( 5/2 + 4/11 + 3/22 + 1/30 + 13/60 )`

   `⇔ 13/28 . x = 1/7 . [ ( 5/2 + 1/30 + 13/60 ) + ( 4/11 + 3/22 ) ]`

   `⇔ 13/28 . x = 1/7 . [ ( 150/60 + 2/60 + 13/60 ) + ( 8/22 + 3/22 ) ]`

   `⇔ 13/28 . x = 1/7 . [ 11/4 + 1/2 ]`

   `⇔ 13/28 . x = 1/7 . [ 11/4 + 2/4 ]`

   `⇔ 13/28 . x = 1/7 . 13/4`

   `⇔ 13/28 . x = 13/28`

   `⇔ x = 13/28 : 13/28`

   `⇔ x = 1`

   Vậy , `x = 1 .`

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2. Đáp án:

   `13/28 × x = 1/7 × [555/222 + 4444/12221 + 33333/244442 + 11/330 + 13/60]`

   `-> 13/28 × x = 1/7 × [5/2 + 4/11 + 3/22 + 1/30 + 13/60]`

   `-> 13/28 × x = 1/7 × [(5/2 + 1/30 + 13/60) + (4/11 + 3/22)]`

   `-> 13/28 × x = 1/7 × [(150/60 + 2/60 + 13/60) + (8/22 + 3/22)]`

   `-> 13/28 × x = 1/7 × [11/4 + 1/2]`

   `-> 13/28 × x = 1/7 × 13/4`

   `-> 13/28 × x = 13/28`

   `-> x = 13/28 ÷ 13/28`

   `-> x = 1`

   Vậy `x = 1`

    

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