\(\Rightarrow\)X*(3/5+2/7)=31/70

\(\Rightarrow\)X*31/35=31/70

\(\Rightarrow\)X=31/70:31/35

\(\Rightarrow\)X=1/2

\(x.\frac{3}{5}+x.\frac{2}{7}=\frac{31}{70}\)

\(x.\frac{31}{35}=\frac{31}{70}\)

\(x=\frac{1}{2}\)

\(y\times\frac{3}{5}+y\times\frac{2}{7}=\frac{31}{70}\)

\(y\times\left(\frac{3}{5}+\frac{2}{7}\right)=\frac{31}{70}\)

\(y\times\frac{31}{35}=\frac{31}{70}\)

\(y=\frac{31}{70}:\frac{31}{35}\)

\(y=\frac{31\times35}{70\times31}\)

\(y=\frac{35}{70}=\frac{1}{2}\)

Đáp số: \(y=\frac{1}{2}\)

Cách Tiểu học nhé em

y x(3/5+2/7)=31/70

y x 31/35=31/70

y=31/70:31/35

y=1/2

a, (X+7)x8-14=66

=>(X+7)x8=66+14

=>(X+7)x8=80

=>X+7=80:8

=>X+7=10

=>X=10-7

=>X=3

b, 1+2+3+...+X=1711

<=>(X+1)xX:2=1711

=>(X+1)xX=1711x2

=>(X+1)xX=3422=59x58

Vì x<x+1 và (x+1)-x=1

=>x=58

c, X+3/5+Xx2/7=31/70

<=>Xx(1+2/7)+3/5=31/70

=>Xx9/7=31/70-3/5

=>Xx9/7=-11/70

=>X=-11/70:9/7

=>X=-11/90

d, 1/7+6/7xX=1/7

=>6/7xX=1/7-1/7

=>6/7xX=0

=>X=0:6/7

=>X=0

Chúc bạn học giỏi nha!!!

K cho mik với nhé cung bảo bình

a) x*4+2,7=22,7      

4x = 20

x=5

b)49,8-x:2,4=29,8    

x:2,4 = 20

x = 48

c)1/7+2/5*x=3/7      

2/5 * x = 2/7

x=5/7

d)x*4+x*15=1919    

x* 19 = 1919

x= 101

e)x*0,7-x*0,2=28      

x* 0,5 = 28

x= 56

f)x*3/5+x*2/7=31/70

x * 31/35 = 31/70

x= 1/2

\(x\times\frac{3}{5}+x\times\frac{2}{7}=\frac{31}{70}\)

\(x\times\left(\frac{3}{5}+\frac{2}{7}\right)=\frac{31}{70}\)

\(x\times\frac{31}{35}=\frac{31}{70}\)

\(x=\frac{31}{70}:\frac{31}{35}\)

\(x=\frac{1}{2}\)

1/2 BAN NHA 

TA LẤY X*(3/5+2/7)=31/70

X*31/35=31/70

X=31/70:31/35

X=1/2

a) (x.7 +8):5=10

x.7 +8= 10.5=50

x.7= 50-8=42

x= 42:7=6

b) 280: (7+3.x)=4

7+3.x= 4.280= 1120

3.x= 1120-7 =1113

x= 1113: 3= 371

c)  (x.5) .19:13= 57

(x.5). 19= 57.13= 741

x.5= 741: 19= 39

x= 39:5 =7,8

d)  6.(28-8).x = 72

20.x= 72:6= 12

x= 12: 20= 0,6

e) 4. (36-4.x)= 3,2

36-4.x= 32:4= 0,8

-4.x= 0,8- 36= -35,2

x= -35,2 : -4 = 8,8

f) (x-15).3 :12= 6

(x-15).3 = 6. 12= 72

x-15= 72: 3= 24

x= 24+ 15= 39

g)  (x:4+ 6) . 7 = 70

x:4+6= 70:7= 10

x:4= 10-6= 4

x= 4.4 = 16

h)  (x:2+50) :5= 12

x:2+ 50= 12.5= 60

x:2= 60-50= 10

x= 10.2=20

l) 5.(7+3.x)= 140

7+3.x= 140:5 = 28

3.x= 28-7 =21

x= 21: 3= 7

k cho mình nhe

7/4 tru 4/3 nhan y bang 5/19
 

\(\frac{x}{\frac{1}{2}}+\frac{x}{\frac{1}{3}}+x=42\)

\(\Rightarrow\frac{x}{\frac{3}{6}}+\frac{x}{\frac{2}{6}}+\frac{x}{\frac{6}{6}}=42\)

\(\Rightarrow\frac{x}{\frac{3}{6}+\frac{2}{6}+\frac{6}{6}}=42\)

\(\Rightarrow\frac{x}{\frac{11}{6}}=42\)

\(\Rightarrow x=77\)

\(x.\frac{4}{7}+x.\frac{2}{3}+x.\frac{3}{7}=\frac{11}{5}\)

\(\Rightarrow x.\left(\frac{4}{7}+\frac{3}{7}+\frac{2}{3}\right)=\frac{11}{5}\)

\(\Rightarrow x.\frac{5}{3}=\frac{11}{5}\)

\(\Rightarrow x=\frac{33}{25}\)

\(\left(\frac{31}{5}-x\right):\frac{2}{3}=\frac{7}{6}\)

\(\Rightarrow\frac{31}{5}-x=\frac{7}{9}\)

\(\Rightarrow x=\frac{244}{45}\)

\(\frac{4}{3}+\left(x-\frac{3}{5}\right)=\frac{21}{2}\)

\(\Rightarrow\frac{4}{3}+x-\frac{3}{5}=\frac{21}{2}\)

\(\Rightarrow x+\frac{11}{5}=\frac{21}{2}\)

\(\Rightarrow x=\frac{83}{10}=8,3\)

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a) Ta có B = \(\left(\frac{2}{15}+\frac{3}{40}+\frac{4}{96}+\frac{5}{204}+\frac{6}{391}\right).x.\left(x-1\right)=\frac{20}{69}\)

         => \(\left(\frac{2}{3.5}+\frac{3}{5.8}+\frac{4}{8.12}+\frac{5}{12.17}+\frac{6}{17.23}\right).x.\left(x-1\right)=\frac{20}{69}\)

         => \(\left(\frac{1}{3}-\frac{1}{5}+\frac{1}{5}-\frac{1}{8}+\frac{1}{8}-\frac{1}{12}+\frac{1}{12}-\frac{1}{17}+\frac{1}{17}-\frac{1}{23}\right).x.\left(x-1\right)=\frac{20}{69}\)

        => \(\left(\frac{1}{3}-\frac{1}{23}\right).x.\left(x-1\right)=\frac{20}{69}\)

        => \(\frac{20}{69}.x.\left(x-1\right)=\frac{20}{69}\)

       => \(x.\left(x-1\right)=\frac{20}{69}:\frac{20}{69}\)

      => \(x.\left(x-1\right)=1\)

      => \(x\in\varnothing\) 

a)  \(\left(\frac{1}{4}+\frac{1}{28}+\frac{1}{70}+....+\frac{1}{8554}\right).x=\frac{31}{94}\)

=> \(\left(\frac{1}{1.4}+\frac{1}{4.7}+\frac{1}{7.10}+...+\frac{1}{91.94}\right).x=\frac{31}{94}\) 

=> \(\frac{1}{3}.\left(\frac{3}{1.4}+\frac{3}{4.7}+\frac{3}{7.10}+...+\frac{3}{91.94}\right)=\frac{31}{94}\)

=> \(\frac{1}{3}.\left(1-\frac{1}{4}+\frac{1}{4}-\frac{1}{7}+\frac{1}{7}-\frac{1}{10}+...+\frac{1}{91}-\frac{1}{94}\right).x=\frac{31}{94}\)

=> \(\frac{1}{3}.\left(1-\frac{1}{94}\right).x=\frac{31}{94}\)

=> \(\frac{1}{3}.\frac{93}{94}.x=\frac{31}{94}\)

=> \(\frac{31}{94}.x=\frac{31}{94}\)

=> \(x=\frac{31}{94}:\frac{31}{94}\)

=> \(x=1\)