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

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

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

\(\Leftrightarrow y=\frac{1}{2}\)

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

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

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

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

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

X x 3/5+ Xx 3/7=31/70

=>X x (3/5+3/7)=31/70

=>X x 36/35=31/70

=>X=31/70:36/35

=>X=31/72

X x 3/5+ Xx 3/7=31/70

=>X x (3/5+3/7)=31/70

=>X x 36/35=31/70

=>X=31/70:36/35

=>X=31/72

X x 3/5+ Xx 3/7=31/70

=>X x (3/5+3/7)=31/70

=>X x 36/35=31/70

=>X=31/70:36/35

=>X=31/72

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

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

x*31/35      =31/70

         x       =31/70 :31/35

         x        = 1/2

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

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

\(x\left(\frac{21}{35}+\frac{10}{35}\right)=\frac{31}{70}\)

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

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

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

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

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

vay \(x=\frac{1}{2}\)

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

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

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

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

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

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

1/2

ban nhe

tk nhe

xin do