Tìm x: A)2/3.x-4/7=1/8 B)2/7-8/9.x=2/3 C)4/7+5/9:x=1/5 Đ)2/5-2/5.x=2/4 E)(2,8.x-32:2/3=90 F)(4,5-3.x).11/4=11/4 Đ)

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1. Đáp án:

   a) 2/3. x – 4/7 = 1/8

       2/3. x = 1/8 + 4/7 

       2/3. x = 39/56

       x = 39/56 : 2/3

       x = 117/112

   b) 2/7 – 8/9. x = 2/3

       8/9. x = 2/7 – 2/3

       8/9. x = -8/21

       x = -8/21 : 8/9

       x = -3/7

   c) 4/7 + 5/9: x = 1/5

       5/9: x = 1/5 – 4/7

       5/9: x = -13/35

       x = 5/9 : ( -13/35 )

       x = -175/117

   d) 2/5 – 2/5. x = 2/4

       2/5. x = 2/5 – 2/4

       2/5. x = -1/10

       x = -1/4

   e) (2,8. x – 32) : 2/3 = 90

        2,8. x – 32 = 90 . 2/3

        2,8. x – 32 = 60

        2,8. x = 60 + 32

        2,8. x = 92

        x = 230/7

   f) (4,5 – 3. x). 11/4 = 11/4

       4,5 – 3. x = 11/4 : 11/4

       4,5 – 3. x = 1

       3. x = 4,5 – 1

       3. x = 3,5

       x = 7/6

    

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