\(\frac{30x+40}{x}=1500:30\)

\(\frac{30x+40}{x}=50\)

Suy ra 30x+40= 50.x

40= 50x- 30x

40= 20x

x=40:20=2

\(1500:\frac{30x+40}{x}=30\)

\(\frac{30x+40}{x}=1500:30\)

\(\frac{30x+40}{x}=50\)

\(\Rightarrow30x+40=50x\)

\(30x+40-50x=0\)

\(40+\left(30x-50x\right)=0\)

\(40-20x=0\)

\(20\left(20-x\right)=0\)

\(\Rightarrow20-x=0\)

\(x=20\)

Vậy x = 20

\(1500:\left[\left(30x+40\right):x\right]=30\)

\(\Leftrightarrow\left(30x+40\right):x=50\)

\(\Leftrightarrow30x+40=50x\)

\(\Leftrightarrow50x-30x=40\)

\(\Leftrightarrow20x=40\)

\(\Leftrightarrow x=2\)

Vậy ..

1500 : [ ( 30x + 40 ) : x ] = 30

[ ( 30x + 40 ) : x ] = 1500 : 30

[ ( 30x + 40 ) : x ] = 50

( 30x + 40 ) = 50 . x

( 30x + 40 ) = 50x

40 = 50x - 30x

40 = 20x

x = 40 : 20

x = 2

Vậy x = 2

a, 

3x + 3 - [7x+4] = 7 + [4x-1]

=> 3x + 3 - x - 4 = 7 + 4x - 1

=> 2x - 1 = 6 + 4x

=> 2x - 4x = 6 + 1

=> -2x = 7

=> x = -7/2

b,

3^x+1 + 3^x+3 =810

=> 3^x+1[1 + 3²] = 810

=> 3^x+1 = 810 / 10

=> 3^x+1 = 81

=> x = 4

c, \(1\frac{1}{2}:\left[\frac{1}{2}-\frac{1}{3}\right]-x=5\)

\(\Rightarrow\frac{3}{2}:\frac{1}{6}-x=5\Leftrightarrow9-x=5\)

\(\Leftrightarrow x=4\)

d,

\(2,4:\left[25\%+\frac{x}{40}\right]-\frac{12}{15}=3\frac{1}{5}\)

\(\Rightarrow\frac{12}{5}:\left[\frac{1}{4}+\frac{x}{40}\right]-\frac{12}{15}=\frac{16}{5}\)

\(\Leftrightarrow\frac{12}{5}:\left[\frac{10}{40}+\frac{x}{40}\right]=\frac{16}{5}+\frac{12}{15}\Leftrightarrow\frac{12}{5}:\left[\frac{10}{40}+\frac{x}{40}\right]=4\)

\(\Rightarrow\frac{10+x}{40}=\frac{12}{5}:4\Leftrightarrow\frac{10+x}{40}=\frac{3}{5}\)

\(\Rightarrow\frac{10+x}{40}=\frac{24}{40}\Leftrightarrow10+x=24\Rightarrow x=14\)

a) 3x + 3 - ( x + 4 ) = 7 + ( 4x - 1 )

3x + 3 - x - 4 = 7 + 4x - 1

2x - 1 = 6 + 4x

-2x  = 7

\(\Rightarrow\)x = \(\frac{-7}{2}\)

b) 3^x+1 + 3^x+3 = 810

3^x . 3 + 3^x . 3³ = 810

3^x . ( 3 + 3³ ) = 810

3^x . 30 = 810

3^x = 810 : 30

3^x = 27

3^x = 3³

\(\Rightarrow\)x = 3

c) \(1\frac{1}{2}:\left(\frac{1}{2}-\frac{1}{3}\right)-x=5\)

\(\frac{3}{2}:\left(\frac{1}{2}-\frac{1}{3}\right)-x=5\)

\(\frac{3}{2}:\frac{1}{6}-x=5\)

\(9-x=5\)

\(\Rightarrow x=9-5\)

\(\Rightarrow x=4\)

d) 2,4 : ( 25% + \(\frac{x}{40}\)) - \(\frac{12}{15}\)= \(3\frac{1}{5}\)

\(\frac{12}{5}\) : ( \(\frac{1}{4}\)+ \(\frac{x}{40}\)) - \(\frac{12}{15}\)= \(\frac{16}{5}\)

\(\frac{12}{5}:\left(\frac{1}{4}+\frac{x}{40}\right)=\frac{16}{5}+\frac{12}{15}\)

\(\frac{12}{5}:\left(\frac{1}{4}+\frac{x}{40}\right)=4\)

\(\frac{1}{4}+\frac{x}{40}=\frac{12}{5}:4\)

\(\frac{1}{4}+\frac{x}{40}=\frac{3}{5}\)

\(\frac{x}{40}=\frac{3}{5}-\frac{1}{4}\)

\(\frac{x}{40}=\frac{7}{20}\)

\(\Rightarrow\frac{x}{40}=\frac{14}{40}\)

\(\Rightarrow x=14\)

1500:[(30x+40):x]=30

=>(30x+40):x=1500:30

=>30x:x+40:x=50

=>30+40:x=50

=>40:x=50-30

=>40:x=20

=>x=40:20

=>x=2

thiếu j              

ko chia đc bạn nha

nếu chia thì x tương đương -1,33422281521

Bài 1 : Tính nhẩm:

a) 1213 - 997 = (1213 + 3 ) - ( 997 + 3 )

                       = 1216 + 1000

                       = 2216

b) 28 . 25 = ( 28 : 4 ) . ( 25 . 4 )

                = 7 . 100

                = 700

c) 3000 : 125 = ( 3000 . 4 ) . ( 125 . 4 )

                      = 12000 . 500

                      = 24

d) 156 : 12 = ( 156 . 5 ) : ( 12 . 5 )

                  = 780 : 60

                  = 13

Bài 2 : Tìm x, biết :

a) x - 280 : 35 = 5 . 54

    x - 280 : 35 = 270

    x - 280 = 270 . 35

    x - 280 = 9450

           x   = 9450 + 280

           x = 9730

b) ( x - 280 ) : 35 = 56 : 5

                      x = 56 : 5 dư nên x bằng quả bí. Mk ko thích suy nghĩ

c) x : 15 + 42 = 13 + 25 . 8

    x : 15 + 4 = 213

    x : 15 = 213 - 4

    x : 15 = 209

          x = 209 . 15

          x = 3135

d) 3636 : ( 12x - 91 ) = 36

    12x - 91 = 3636 : 36

    12x - 91 = 11

     12x = 11 + 91

     12x = 102

         x = 102 : 12

         x = 8,5

e) ( x : 23 + 45 ) . 67 = 8911

      x : 23 + 45 = 8911 : 67

      x : 23 + 45 = 133

      x : 23 = 133 - 45

      x : 23 = 88 . 23

                =  2024

f) 64x + 36x = 1500

x( 64 + 26 ) = 1500

x . 90 = 1500

    x = 1500 : 90

    x = 150 / 90

x- 280:35=5.54

x-8=270

x=287

hung pham tien bn vào câu hỏi tương tự đi , có đấy 

 **** cho minh 

( 30.x +40)/x=1500/2=750

30x+40=750x

30x-750x=-40

-720x=-40

x=1/18

có đúng k bạn lớp 6 sợ giải thế sai