\(a,\left(x+\frac{1}{2}\right)+\left(x+\frac{1}{4}\right)+\left(x+\frac{1}{8}\right)+\left(x+\frac{1}{16}\right)=1\)

\(\Leftrightarrow x+\frac{1}{2}+x+\frac{1}{4}+x+\frac{1}{8}+x+\frac{1}{16}=1\)

\(\Leftrightarrow\left(x+x+x+x\right)+\left(\frac{1}{2}+\frac{1}{4}+\frac{1}{8}+\frac{1}{16}\right)=1\)

\(\Leftrightarrow4\times x+\frac{15}{16}=1\)

\(\Leftrightarrow4\times x=1-\frac{15}{16}\)

\(\Leftrightarrow4\times x=\frac{1}{16}\)

\(\Leftrightarrow x=\frac{1}{16}\div4\)

\(\Leftrightarrow x=\frac{1}{64}\)

\(b,x-\frac{20}{11.13}-\frac{20}{13.15}-...-\frac{20}{53.55}=\frac{3}{11}\)

\(\Leftrightarrow x-\left(\frac{20}{11.13}+\frac{20}{13.15}+...+\frac{20}{53.55}\right)=\frac{3}{11}\)

\(\Leftrightarrow x-\left[715\times\left(\frac{1}{11}-\frac{1}{13}-\frac{1}{13}+...+\frac{1}{55}\right)\right]=\frac{3}{11}\)

\(\Leftrightarrow x-\left[715\times\left(\frac{1}{11}-\frac{1}{55}\right)\right]=\frac{3}{11}\)

\(\Leftrightarrow x-\left[715\times\frac{4}{55}\right]=\frac{3}{11}\)

\(\Leftrightarrow x-52=\frac{3}{11}\)

\(\Leftrightarrow x=\frac{3}{11}+52\)

\(\Leftrightarrow x=\frac{575}{11}\)

a.    12,5 - \(x\) = \(x\) + 12

 \(x\) + 12  + \(x\) = 12,5

  \(x\) x 1 + \(x\) x 1 = 12,5 - 12

  \(x\) x (1 + 1) = 0,5

  \(x\) x 2         = 0,5

  \(x\)               = 0,5 : 2

  \(x\)              = 0,25

b, 8 \(\times\) \(x\) + 3 \(\times\) \(x\) + 2 \(\times\) \(x\) = 20

   \(x\) \(\times\) (8 + 3 + 2)  =20

   \(x\) \(\times\) 13 = 20

  \(x\)          = 20 : 13

  \(x\)          = \(\dfrac{20}{13}\)

b, 8 $\times$ $x$ + 3 $\times$ $x$ + 2 $\times$ $x$ = 20

   $x$ $\times$ (8 + 3 + 2)  =20

   $x$ $\times$ 13 = 20

  $x$          = 20 : 13

  $x$          = 20131320​
 

giúp mk với nha

\(\text{a/96-3(x+1)=42}\)

\(3\left(x+1\right)=54\)

\(x+1=54:3\)

\(x+1=18\)

\(\Rightarrow x=17\)

\(\text{b/2.x-18=20}\)

\(2x=38\)

\(x=38:2\)

\(x=19\)

\(\text{c/134-5.(x+4)=34}\)

\(5\left(x+4\right)=100\)

\(x+4=100:5\)

\(x+4=20\)

\(\Rightarrow x=16\)

học tốt

a) 96-3(x+1)=42

3(x+1)=96-42

3(x+1)=54

x+1=54:3

x+1=18

x=18-1

Vậy x=17

b) 2x-18=20

2x=20+18

2x=38

x=38:2

x=19

Vậy x=19.

c) 134-5(x+4)=34

5(x+4)=134-34

5(x+4)=100

x+4=100:5

x+4=20

x=20-4

x=16

Vậy x=16.

a) 96-3(x+1)=42

          3(x+1)=96-42

          3(x+1)=54

               x+1=54:3

               x+1=18

                   x=18-1

                   x=17

Vậy x=17

b)2.x-18=20

   2.x     =20+18

   2.x     =38

      x     =38:2

      x     =19

Vậy x=19

c)134-5.(x+4)=34

          5.(x+4)=134-34

          5.(x+4)=100

              x+4 =100:5

              x+4 =20

                  x =20-4

                  x =16

Vậy x=16
 

Bài 3 : 

b) Ta có 1+ 2 + 3 +4 + ...+ x =15

Nên \(\frac{x\left(x+1\right)}{2}=15\)

\(x\left(x+1\right)=30\)

=> \(x\left(x+1\right)=5.6\)

=> x = 5

Bài 2:

h; \(\dfrac{2}{3}\)\(x\)  + 50% + \(x\) = \(\dfrac{1}{10}\)

    \(\dfrac{2}{3}\)\(x\) + \(\dfrac{1}{2}\)  + \(x\) = \(\dfrac{1}{10}\)

    (\(\dfrac{2}{3}\)\(x\) + \(x\)) + \(\dfrac{1}{2}\) = \(\dfrac{1}{10}\)

     \(x\) \(\times\) (\(\dfrac{2}{3}\) + 1) + \(\dfrac{1}{2}\) = \(\dfrac{1}{10}\)

      \(x\) \(\times\) \(\dfrac{5}{3}\) + \(\dfrac{1}{2}\) = \(\dfrac{1}{10}\)

      \(x\) \(\times\) \(\dfrac{5}{3}\) = \(\dfrac{1}{10}\) - \(\dfrac{1}{2}\)

      \(x\) \(\times\) \(\dfrac{5}{3}\) = \(\dfrac{-2}{5}\)

      \(x\)         = \(\dfrac{-2}{5}\): \(\dfrac{5}{3}\)

      \(x\)         =   - \(\dfrac{6}{25}\) 

Lớp 5 chưa học số âm em nhé. 

Bài 3:

a;  (\(x\) + 2) + (\(x\) + 4) + (\(x+6\)) + ... + (\(x+100\)) = 6000

     \(x\) + 2 + \(x\) + 4 + ... + \(x\) + 2 + 4 + 6 + ... + 100 = 6000

    (\(x\) + \(x\) + \(x\) + ... + \(x\)) + (2 + 4 + ... + 100) = 6000

     Xét dãy số 2; 4; ...;100;

Đây là dãy số cách đều với khoảng cách là: 4 - 2 = 2

Số số hạng của dãy số trên là: (100 - 2) : 2 + 1 = 50 (số)

 Theo bài ra ta có:

   \(x\) \(\times\) 50 + (100 + 2) \(\times\) 50 : 2 = 6000

   \(x\) \(\times\) 50 + 102 x 50 : 2 = 6000

    \(x\) \(\times\) 50 + (102 : 2) x 50 = 6000

    \(x\) x 50 + 51 x 50 = 6000

   \(x\) \(\times\) 50 + 2550 = 6000

    \(x\) x 50 = 6000 - 2550

    \(x\) x 50 = 3450

    \(x\) x 50 = 3450

   \(x\)           = 3450 : 50

   \(x\)           = 69

a,3x-3+6x-12=5

9x-15=5

9x=20

x=20/9

b,3x-6+6x-6=6

9x-12=6

9x=18

x=2

c,4x+4+5x+10=3x+20

9x+14=3x+20

9x-3x=6

6x=6

x=1

a) 3.(x-1) + 6.(x-2) = 5

3.x - 3 + 6.x - 12 = 5

9.x - 15 = 5

9.x = 5 + 15

9.x = 20

x = \(\frac{20}{9}\)

Vậy x = \(\frac{20}{9}\)

b) 3.(x-2) + 6.(x-1) = 6

  3.x - 6 + 6.x - 6 = 6

9.x - 12 = 6

9.x = 6 + 12

9.x = 18

x = 18 : 9

x = 2

Vậy x = 2

c) 4.(x+1) + 5.(x+2) = 3.x +20

4.x +4 +5.x +10 = 3.x +20

9.x + 14 = 3.x +20

9.x - 3.x = 20 - 14

6.x = 6

x = 6 : 6

x = 1

Vậy x = 1

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

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