a: =>x+7/4=6:2/3=9

=>x=29/4

b: =>x:5/3=7/5

=>x=7/5*5/3=7/3

c:=>x+1/6=5/3

=>x=10/6-1/6=3/2

d: =>x+4/5=4/5+3/7+3/5

=>x=3/7+3/5=36/35

e: =>x/35=4/5-5/7=3/35

=>x=3

f: =>13/28+x=1/2

=>x=1/28

g: =>1/3-x=1/9

=>x=2/9

a: x*3/4=1/5

=>x=1/5:3/4=1/5*4/3=4/15

b: x*3/7=2/5

=>x=2/5:3/7=2/5*7/3=14/15

c: 1/3+2/9=2/12x

=>1/6x=3/9+2/9=5/9

=>x=5/9*6=30/9=10/3

d: 4/15*x-2/3=1/5

=>4/15*x=2/3+1/5=10/15+3/15=13/15

=>4x=13

=>x=13/4

e: x:1/7=2/3

=>x=2/3*1/7=2/21

f: 1/9:x=7/3

=>x=1/9:7/3=1/9*3/7=3/63=1/21

j: 1/4+5/12=8/3:x

=>8/3:x=3/12+5/12=8/12=2/3

=>x=4

h: =>7/4:x=1/5+1/2=7/10

=>x=7/4:7/10=10/4=5/2

\(x\left(45+1+54\right)=9872\)

\(x\times100=9872\)

\(x=9872:100\)

\(x=98.72\)

X x45 + X +X x 54 =9872

X x45 + Xx1 +Xx54=9872

X x ( 45 + 1 + 54)   = 9872

X x           100         = 9872

X                             = 9872 : 100

X                             = 98,72

98,72

\(a,x=\dfrac{1}{2}-\dfrac{2}{5}\)

\(x=\dfrac{1}{10}\)

\(b,x+\dfrac{3}{7}=\dfrac{7}{10}\)

\(x=\dfrac{7}{10}-\dfrac{3}{7}\)

\(x=\dfrac{19}{70}\)

\(c,19-x=\dfrac{17}{20}\)

\(x=19-\dfrac{17}{20}\)

\(x=\dfrac{363}{20}\)

a,1/10

b,19/70

c,18/4

x=36320

\(a,\dfrac{-1}{8}=\dfrac{3}{x}\\ \dfrac{3}{-24}=\dfrac{3}{x}\\ x=-24\\ b,\dfrac{x}{3}=\dfrac{3}{x}\\ x.x=3.3\\ x^2=9\\ x=\pm3\\ c,\dfrac{3}{4}.x=1\dfrac{1}{2}\\ \dfrac{3}{4}.x=\dfrac{3}{2}\\ x=\dfrac{3}{2}:\dfrac{3}{4}\\ x=2\\ d,x-\dfrac{3}{10}=\dfrac{7}{15}:\dfrac{3}{5}\\ x-\dfrac{3}{10}=\dfrac{7}{9}\\ x=\dfrac{7}{9}+\dfrac{3}{10}\\ x=\dfrac{97}{90}\\ e,\dfrac{-4}{7}-x=\dfrac{-8}{3}.\dfrac{3}{7}\\ \dfrac{-4}{7}-x=\dfrac{-8}{7}\\ x=\dfrac{-4}{7}+\dfrac{8}{7}\\ x=\dfrac{4}{7}\\ \)

f: =>x*4/7=1/5+2/3=3/15+10/15=13/15

=>x=91/60

g: =>1/3:3x=1/5-2/3=-7/15

=>3x=-5/7

=>x=-5/21

h: =>7/8x=-1/9

=>x=-1/9:7/8=-1/9*8/7=-8/63

j: =>(2,8x-50)=34

=>2,8x=84

=>x=30

a) \(\dfrac{4}{7}\times x=\dfrac{5}{9}+\dfrac{1}{5}=\dfrac{34}{45}\)

\(x=\dfrac{34}{45}:\dfrac{4}{7}=\dfrac{119}{90}\)

b) \(\dfrac{11}{15}:x=\dfrac{2}{3}-\dfrac{9}{15}=\dfrac{1}{15}\)

\(x=\dfrac{11}{15}:\dfrac{1}{15}=11\)

a) 4/7 x X - 1/5 = 5/9   

     4/7 x X         = 5/9 + 1/5

     4/7 x X         =  34/45

             X          = 34/45 : 4/7

             X          =  119/90

 b)9/15 + 11/15 : X = 2/3

               11/15 : X = 2/3 - 9/15

               11/15 : X =  1/15

                           X = 11/15 : 1/5 

                           X = 11

a,3/4 . (-5/12)+3/4.(-7/12)

` 3/4 . [ - ( 5/12 + 7/12  ) ] `

`3/4 . (-1) = -3/4 `

`2/3 . x - 0,5 = 3/4 `

`        x - 0,5 = 3/4 - 2/3 `

`        x-0,5 = 1/12 `

`        x =       1/12 + 0,5 `

`        x= 7/12 `

a, 3/4 . (-5/12)+3/4.(-7/12) 

= 3/4 . [(-5/12) + (-7/12)]

= 3/4 . (-1)

= -3/4

----------------------------------------------------------------------------

a, 2/3 .x-0,5=3/4

2/3 . x = 3/2 + 0,5

2/3 . x = 2 

x = 2 : 2/3

x = 3 

vậy x = 3

Bài 2:

a: =>2/3x=3/4+1/2=3/4+2/4=5/4

=>x=5/4:2/3=5/4*3/2=15/8

b:=>-2x+4=3x-12

=>-5x=-16

=>x=16/5