Ta có (7+x)/12=2/3

  suy ra 3(7+x)=24

  suy ra 7+x=8

          x=1

Ta có (25-x)/18=1/2

suy ra 2(25-x)=18

suy ra 25-x=9

         x=16

a,x=-76

b,x=441

128 - 3.(x+4) = 25-2

128 - 3.x - 12 = 23

128 - 12 -3.x = 23

116 - 3.x = 23

3.x = 93

x = 31

các bài còn lại bn dựa vào phần a mak lm nha!
 

128-3(x+4)=25-2

128-3(x+4)=23

       3(x+4)=128-23

       3(x+4)=105

         (x+4)=105:3

           x+4=35

           x    =35-4

           x    =31

3/5-1/4:x=25/100

1/4:x=25/100+3/5

1/4:x=17/20

      x=17/20x1/4

      x=17/80

Vậy x=17/80

cam on ban nhieu nhe 

\(6-2\left(x-1\right)=4\)

\(\Rightarrow2\left(x-1\right)=6-4\)

\(\Rightarrow2\left(x-1\right)=2\)

\(\Rightarrow x-1=1\)

\(\Rightarrow x=1+1=2\)

________________

\(2\cdot\left(x-2\right)+1=7\)

\(\Rightarrow2\cdot\left(x-2\right)=7-1\)

\(\Rightarrow2\cdot\left(x-2\right)=6\)

\(\Rightarrow x-2=3\)

\(\Rightarrow x=3+2=5\)

_______________

\(\left(2\cdot x-3\right)+4=9\)

\(\Rightarrow2\cdot x-3=5\)

\(\Rightarrow2\cdot x=3+5\)

\(\Rightarrow2\cdot x=8\)

\(\Rightarrow x=\dfrac{8}{2}=4\)

________________

\(\left(3\cdot x-2\right)-1=3\)

\(\Rightarrow3\cdot x-2=3+1\)

\(\Rightarrow3\cdot x-2=4\)

\(\Rightarrow3\cdot x=6\)

\(\Rightarrow x=\dfrac{6}{3}=2\)

a: =>2(x-1)=2

=>x-1=1

=>x=2

b: =>2(x-2)=6

=>x-2=3

=>x=5

c; =>2x-3=5

=>2x=8

=>x=4

d: =>3x-2=4

=>3x=6

=>x=2

e: =>2(6-x)=4

=>6-x=2

=>x=4

f: =>x-2=5

=>x=7

g: =>10-2x=4

=>2x=6

=>x=3

h: =>2x+4=3

=>2x=-1

=>x=-1/2

j: =>x+2=12

=>x=10

l: =>2x+3=3

=>2x=0

=>x=0

\(\frac{2}{3}:\frac{x}{5}+\frac{5}{7}=\frac{2}{7}:\frac{3}{5}+\frac{9}{10}\)

\(\frac{2}{3}.\frac{5}{x}=\frac{2}{7}.\frac{5}{3}+\frac{9}{10}-\frac{5}{7}\)

\(\frac{10}{3}:x=\frac{10}{21}+\frac{9}{10}-\frac{5}{7}=\frac{100+189-150}{210}=\frac{139}{210}\)

\(x=\frac{700}{139}\)