Tìm x a, 71- ( 33+x)=26 b, 45 – (x+9)=6 c,(x+7)-25=13 d, 198-(x+4)=120 e, [(6x-39):7]×4=12

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1. $\text{a) 71 – (33 + x) = 26}$

   $\text{⇒ 33 + x = 71 – 26}$

   $\text{⇒ 33 + x = 45}$

   $\text{⇒ x = 45 – 33}$

   $\text{⇒ x = 12}$

   $\text{Vậy x = 12.}$

   $\text{b) 45 – (x + 9) = 6}$

   $\text{⇒ x + 9 = 45 – 6}$

   $\text{⇒ x + 9 = 39}$

   $\text{⇒ x = 39 – 9}$

   $\text{⇒ x = 30}$

   $\text{Vậy x = 30.}$

   $\text{c) (x + 7) – 25 = 13}$

   $\text{⇒ x + 7 = 13 + 25}$

   $\text{⇒ x + 7 = 38}$

   $\text{⇒ x = 38 – 7}$

   $\text{⇒ x = 31}$

   $\text{Vậy x = 31.}$

   $\text{d) 198 – (x + 4) = 120}$

   $\text{⇒ x + 4 = 198 – 120}$

   $\text{⇒ x + 4 = 78}$

   $\text{⇒ x = 78 – 4}$

   $\text{⇒ x = 74}$

   $\text{Vậy x = 74.}$

   $\text{e) [(6x – 39) ÷ 7] × 4 = 12}$

   $\text{⇒ (6x – 39) ÷ 7 = 12 ÷ 4}$

   $\text{⇒ (6x – 39) ÷ 7 = 3}$

   $\text{⇒ 6x – 39 = 3 × 7}$

   $\text{⇒ 6x – 39 = 21}$

   $\text{⇒ 6x = 21 + 39}$

   $\text{⇒ 6x = 60}$

   $\text{⇒ x = 60 ÷ 6}$

   $\text{⇒ x = 10}$

   $\text{Vậy x = 10.}$

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2. $a.71-(33+x)=26 \\⇔71-33-x=26 \\⇔38-x=26 \\⇔x=12 \\Vậy\ x=12 \\b.45-(x+9)=6 \\⇔45-x-9=6 \\⇔36-x=6 \\⇔x=30 \\Vậy\ x=30 \\c.(x+7)-25=13 \\⇔x+7-25=13 \\⇔x-18=13 \\⇔x=31 \\Vậy\ x=31 \\d.198-(x+4)=120 \\⇔198-x-4=120 \\⇔194-x=120 \\⇔x=74 \\Vậy\ x=74 \\e.[(6x-39):7].4=12 \\⇔(6x-39):7=3 \\⇔6x-39=21 \\⇔6x=60 \\⇔x=10 \\Vậy\ x=10$

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