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222-9+11+12:2*14+14 = ? ( )

Toán Lớp 6: tìm x biết a.25-(30+x)=x-(27-8) b.(x-12)-15=(20-7)-(18+x) giúp mik mik vote 5 sao lun

Toán Lớp 6: tìm x biết
a.25-(30+x)=x-(27-8)
b.(x-12)-15=(20-7)-(18+x)
giúp mik mik vote 5 sao lun

Comments ( 2 )

  1. a) 25 – (30 + x) = x – (27 – 8)
    => 25 – (30 + x) = x – 19
    => 25 – 30 + x = x – 19 (Phá ngoặc theo quy tắc dấu ngoặc)
    => -x – x = -19 – 25 + 30
    => -2x = -14
    => x = -14 : -2
    => x = 7
    Vậy x = 7
    b) (x – 12) – 15 = (20 – 7) – (18 + x)
    => x – 12 – 15 = 20 – 7 – 18 – x (Phá ngoặc theo quy tắc dấu ngoặc) 
    => x + x = 20 – 7 – 18 + 12 + 15 (Chuyển vế đổi dấu)
    => 2x = 22
    => x = 22 : 2
    => x = 11
    Vậy x = 11

  2. a. 25 – (30 + x) = x – (27 – 8)
        25 – 30 – x = x – 19
                -5 – x = x – 19
                 2x = 19 – (-5)
                 2x = 14
                   x = 14 : 2
                   x = 7
    Vậy  x = 7
    ___________________________________________
    b. (x – 12) – 15 = (20 – 7) – (18 + x)
          x – 12 – 15 = 13 – 18 – x
                 x – 27 = -5 – x
                       2x = -5 + 27
                       2x = 22
                         x = 22 : 2
                         x = 11
    Vậy  x = 11

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222-9+11+12:2*14+14 = ? ( )