a: \(\left[\left(10-x\right)\cdot2+51\right]:3-2=3\)

=>\(\left[2\left(10-x\right)+51\right]:3=5\)

=>\(\left[2\left(10-x\right)+51\right]=15\)

=>\(2\left(10-x\right)=15-51=-36\)

=>10-x=-36/2=-18

=>\(x=10-\left(-18\right)=10+18=28\)

b: \(\left(x-12\right)-15=20-\left(17+x\right)\)

=>\(x-12-15=20-17-x\)

=>\(x-27=3-x\)

=>\(2x=30\)

=>\(x=\dfrac{30}{2}=15\)

c: \(720-\left[41-\left(2x-5\right)\right]=2^3\cdot5\)

=>\(720-\left[41-2x+5\right]=8\cdot5=40\)

=>\(\left[41-2x+5\right]=720-40=680\)

=>-2x+46=680

=>-2x=680-46=634

=>\(x=\dfrac{634}{-2}=-317\)

a) 128 - 3(x + 4) = 23

             3(x + 4) = 128 -23

             3(x + 4) = 105

                x + 4  = 105 : 3

                x + 4  = 35

                x        = 35 - 4

                x        = 31

\(a.128-3\left(x+4\right)=23.\)

\(3\left(x+4\right)=128-23\)

\(3\left(x+4\right)=105\)

\(x+4=105:3=35\)

\(x=35-4=31\)

\(b.\left[\left(4x+28\right)\cdot3+55\right]:5=35\)

\(\left(4x+28\right)\cdot3+55=35\cdot5=175\)

\(\left(4x+28\right)\cdot3=175-55=120\)

\(4x+28=120:3=40\)

\(4x=40-28=12\)

\(x=12:4=3\)

a, \(128-3.\left(x+4\right)=23\)

\(\Rightarrow\) \(3.\left(x+4\right)=105\)

\(\Rightarrow\) \(x+4=35\)

\(\Rightarrow\) \(x=31\)

b, \(\left[\left(4x+28\right).3+55\right]:5=35\)

\(\Rightarrow\) \(\left(4x+28\right).3+55=175\)

\(\Rightarrow\) \(\left(4x+28\right).3=120\)

\(\Rightarrow\) \(4x+28=40\)

\(\Rightarrow\) \(4x=12\)

\(\Rightarrow\) \(x=3\)

 m , Ta có : \(\left(1900-2.x\right):3-32=16\)

 \(\Leftrightarrow\frac{1900-2.x}{35}-32=16\)( Nhân hai vế với 35 ) 

 \(\Leftrightarrow1900-2.x-1120=560\)

  \(\Leftrightarrow780-2.x=560\)

 \(\Leftrightarrow-2.x=560-780\)

\(\Leftrightarrow\) \(-2.x=-220\)

 \(\Rightarrow x=110\)

Vậy x = 110

n, Ta có : \(720:\left[41-\left(2.x-5\right)\right]=2^3.5\)

             \(\Leftrightarrow720:\left(41-2.x+5\right)=8.5\)

              \(\Leftrightarrow720:\left(46-2.x\right)=40\)

              \(\Leftrightarrow\frac{720}{46-2.x}=40\)

              \(\Leftrightarrow\frac{720}{2.\left(23-x\right)}=40\)

               \(\Leftrightarrow\frac{360}{23-x}\)

               \(\Leftrightarrow360=40.\left(23-x\right)\)

               \(\Leftrightarrow9=23-x\)

               \(\Leftrightarrow x=14\)

Vậy x = 14

o, Ta có : \(\left(x-5\right).\left(x^2-4\right)=0\)

             \(\Leftrightarrow\orbr{\begin{cases}x-5=0\\x^2-4=0\end{cases}}\)

              \(\Rightarrow\orbr{\begin{cases}x=5\\x=\pm2\end{cases}}\)

Vậy \(x=5;-2;2\)

a, (17x-25):8=81-65

(17x-25):8=16

17x-25=16:8

17x-25=2

17x=2+25

17x=27

x=27:17

x=27/17

b,720:[41-(2x-5)]=40

41-(2x-5)=720:40

41-(2x-5)=18

2x-5=41-18

2x-5=23

2x=23+5

2x=28

x=28:2

x=14

c,231-(x-6)=103

x-6=231-103

x-6=128

x=128+6

x=134

XEM LẠI GIÙM MÌNH BẠN NHA!

đề bài: (17x-25):8+65= 81

     (17x-25):8=81-65=16

      17x-25= 16 . 8= 128

     17x = 128+25=153

         x = 153:17=9

b, Đề bài 720:[41-(2x-5)]=8.5

              720:[41-(2x-5)]=40

            41-(2x-5)=720:40=18

                2x-5=41-18=23

               2x = 23+5=28

                 x = 28:2= 14

c, 231-(x-6)=1339:13=103

    x-6=231-103=128

     x= 128 + 6= 134

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