a, y \(\times\) \(\dfrac{4}{3}\) = \(\dfrac{16}{9}\)

    y         =    \(\dfrac{16}{9}\) : \(\dfrac{4}{3}\)

    y         = \(\dfrac{4}{3}\)

b, ( y - \(\dfrac{1}{2}\)) + 0,5 = \(\dfrac{3}{4}\)

    y - 0,5 + 0,5 = \(\dfrac{3}{4}\)

   y                   = \(\dfrac{3}{4}\)

c, \(\dfrac{4}{5}-\dfrac{2}{5}y\) = 0,2

   0,8 - 0,4y = 0,2

           0,4y = 0,8 - 0,2

           0,4y  = 0,6

               y = 1,5

d, (y + \(\dfrac{3}{4}\)) \(\times\) \(\dfrac{5}{7}\) = \(\dfrac{10}{9}\)

    y + \(\dfrac{3}{4}\)           = \(\dfrac{10}{9}\) : \(\dfrac{5}{7}\)

   y + \(\dfrac{3}{4}\)            = \(\dfrac{14}{9}\)

y                    = \(\dfrac{14}{9}\) - \(\dfrac{3}{4}\)

 y                   =   \(\dfrac{29}{36}\)

e, y : \(\dfrac{5}{4}\)         = \(\dfrac{9}{5}\)  + \(\dfrac{1}{2}\)

   y : \(\dfrac{5}{4}\)         =   \(\dfrac{23}{10}\)

  y                =      \(\dfrac{23}{10}\)

  y               =   \(\dfrac{23}{8}\)

f, y \(\times\) \(\dfrac{1}{2}\) + \(\dfrac{3}{2}\) \(\times\) y   = \(\dfrac{4}{5}\)

   y \(\times\) ( \(\dfrac{1}{2}+\dfrac{3}{2}\))      =  \(\dfrac{4}{5}\)

   2y                       = \(\dfrac{4}{5}\)

    y                        = \(\dfrac{2}{5}\)

a, (10/3:x).(-5/4)=-10/3

10/3:x=-10/3:(-5/4)

10/3:x=8/3

x=10/3:8/3

x=5/4

b,(-6/5+x):(-18/5)=-1/4

-6/5+x=-1/4.(-18/5)

-6/5+x=9/10

x=9/10-(-6/5)=9/10+6/5

x=21/10

c,-22/15.x+1/3=-2/5

-22/15.x=-2/5-1/3=-11/15

x=-11/15:(-22/15)

x=11/21

d,(0,25-30%x).1/3=-31/6+1/4=-59/12

1/4-3/10x=-59/12:1/3=-59/4

3/10x=1/4-(-59/4)=1/4+59/4=15

x=15:3/10

x=50

e,(0,5x-3/7):1/2=8/7

1/2x=8/7.1/2=4/7

x=4/7:1/2

x=8/7

1) 2(x + 5) + 3(x + 7) = 41
2x + 10 + 3x + 21 = 41
5x + 31 = 41
5x = 10
x = 2
6) 7(x - 1) + 5(3 - x) = 11x - 10
7x - 7 + 15 - 5x = 11x - 10
2x + 8 = 11x - 10
-9x = -18
x = 2

2) 5(x + 6) + 2(x - 3) = 38
5x + 30 + 2x - 6 = 38
7x + 24 = 38
7x = 14
x = 2

7) 4(2 + x) + 3(x - 2) = 12
8 + 4x + 3x - 6 = 12
7x + 2 = 12
7x = 10
x = 10/7

3) 7(5 + x) + 2(x - 10) = 15
35 + 7x + 2x - 20 = 15
9x + 15 = 15
9x = 0
x = 0

8) 5(2 + x) + 4(3 - x) = 10x - 15
10 + 5x + 12 - 4x = 10x - 15
x + 22 = 10x - 15
9x = 37
x = 37/9

4) 3(x + 4) + (8 - 2x) = 22
3x + 12 + 8 - 2x = 22
x + 20 = 22
x = 2

9) 7(x - 2) + 5(3 - x) = 11x - 6
7x - 14 + 15 - 5x = 11x - 6
2x + 1 = 11x - 6
-9x = -7
x = 7/9

5) 4(x + 5) + 3(7 - x) = 49
4x + 20 + 21 - 3x = 49
x + 41 = 49
x = 8

10) 5(3 - x) + 5(x + 4) = 6 + 4x
15 - 5x + 5x + 20 = 6 + 4x
35 = 6 + 4x
4x = 29
x = 29/4

1) 2(x + 5) + 3(x + 7) = 41

2x + 10 + 3x + 21 = 41

5x + 31 = 41

5x = 41 - 31

5x = 10

x = 10 : 5

x = 2

2) 5(x + 6) + 2(x - 3) = 38

5x + 30 + 2x - 6 = 38

7x + 24 = 38

7x = 38 - 24

7x = 14

x = 14 : 7

x = 2

3) 7(5 + x) + 2(x - 10) = 15

35 + 7x + 2x - 20 = 15

9x + 15 = 15

9x = 15 - 15

9x = 0

x = 0

4) 3(x + 4) + (8 - 2x) = 22

3x + 12 + 8 - 2x = 22

x + 20 = 22

x = 22 - 20

x = 2

5) 4(x + 5) + 3(7 - x) = 49

4x + 20 + 21 - 3x = 49

x + 41 = 49

x = 49 - 41

x = 8

6) 7(x - 1) + 5(3 - x) = 11x - 10

7x - 7 + 15 - 5x = 11x - 10

2x - 11x + 8 = -10

-9x = -10 - 8

-9x = -18

x = -18 : (-9)

x = 2

7) 4(2 + x) + 3(x - 2) = 12

8 + 4x + 3x - 6 = 12

7x + 2 = 12

7x = 12 - 2

7x = 10

x = 10/7

8) 5(2 + x) + 4(3 - x) = 10x - 15

10 + 5x + 12 - 4x = 10x - 15

10x - 15 = x + 22

10x - x = 22 + 15

9x = 37

x = 37/9

9) 7(x - 2) + 5(3 - x) = 11x - 6

7x - 14 + 15 - 5x = 11x - 6

11x - 6 = 2x + 1

11x - 2x = 1 + 6

9x = 7

x = 7/9

10) 5(3 - x) + 5(x + 4) = 6 + 4x

15 - 5x + 5x + 20 = 6 + 4x

6 + 4x = 35

4x = 35 - 6

4x = 29

x = 29/4

\(a) \frac{4}{5}.x=\frac{8}{35}\)

\(\implies x= \frac{8}{35}:\frac{4}{5}\)

\(\implies x=\frac{8}{35}.\frac{5}{4}\)

\(\implies x=\frac{2}{7}\). Vậy \(x=\frac{2}{7}\)

\(b) \frac{3}{5}x-\frac{1}{2}=\frac{1}{7}\)

\(\implies \frac{3}{5}x=\frac{1}{7}+\frac{1}{2}\)

\(\implies \frac{3}{5}x=\frac{9}{14}\)

\(\implies x=\frac{9}{14}:\frac{3}{5}\)

\(\implies x=\frac{9}{14}.\frac{5}{3} \)

\(\implies x=\frac{15}{14}\). Vậy \(x=\frac{15}{14}\)

\(c) x-25\% x=0,5\)

\(\implies 75\% x=0,5\)

\(\implies \frac{3}{4}x=\frac{1}{2}\)

\(\implies x=\frac{1}{2}:\frac{3}{4}\)

\(\implies x=\frac{1}{2}.\frac{4}{3}\)

\(\implies x=\frac{2}{3}\). Vậy \(x=\frac{2}{3}\)

\(d) (\frac{1}{24.25}+\frac{1}{25.26}+...+\frac{1}{29.30}).120+x:\frac{1}{3}=-4\)

Có: \(\frac{1}{24.25}+\frac{1}{25.26}+...+\frac{1}{29.30}\)

\(=\frac{1}{24}-\frac{1}{25}+\frac{1}{25}-\frac{1}{26}+...+\frac{1}{29}-\frac{1}{30}\)

\(=\frac{1}{24}-\frac{1}{30}\)

\(=\frac{1}{120}\)

Thay vào ta có: \(\frac{1}{120}.120+x:\frac{1}{3}=-4\)

\(\implies 1+x:\frac{1}{3}=-4\)

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

\(\implies x=-5.\frac{1}{3}\)

\(\implies x=\frac{-5}{3}\). Vậy \(x=\frac{-5}{3}\)

~ Hok tốt a~

\(\frac{4}{5}.x=\frac{8}{35}\)                                                                        \(\frac{3}{5}x-\frac{1}{2}=\frac{1}{7}\)

\(x=\frac{8}{35}:\frac{4}{5}\)                                                                        \(\frac{3}{5}x=\frac{1}{7}+\frac{1}{2}\)

\(x=\frac{8}{35}.\frac{5}{4}\)                                                                          \(\frac{3}{5}x=\frac{9}{14}\)

\(x=\frac{2}{7}\)                                                                                      \(x=\frac{9}{14}:\frac{3}{5}\)

Vậy \(x=\frac{2}{7}\)                                                                               \(x=\frac{9}{14}.\frac{5}{3}\)

\(x-25\%x=0.5\)                                                                   \(x=\frac{15}{14}\)

 \(x-\frac{1}{4}x=\frac{1}{2}\)                                                                   Vậy \(x=\frac{15}{14}\)

\(x\left(1-\frac{1}{4}\right)=\frac{1}{2}\)                                   \(\left(\frac{1}{24.25}+\frac{1}{25.26}+...+\frac{1}{29.30}\right).120+x:\frac{1}{3}=-4\)

\(x=\frac{1}{2}:\frac{3}{4}\)                                       \(\left(\frac{1}{24}-\frac{1}{25}+\frac{1}{25}-\frac{1}{26}+...+\frac{1}{29}-\frac{1}{30}\right).120+x:\frac{1}{3}=-4\)               \(x=\frac{2}{3}\)                                              \(\left(\frac{1}{24}-\frac{1}{30}\right).120+x:\frac{1}{3}=-4\)

Vậy \(x=\frac{2}{3}\)                                        \(\frac{1}{120}.120+x:\frac{1}{3}=-4\)

                                                                   \(1+x:\frac{1}{3}=-4\)

                                                                    \(x:\frac{1}{3}=\left(-4\right)-1\)

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

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

                                                                      \(x=-\frac{5}{3}\)

                                                                    Vậy \(x=-\frac{5}{3}\)

\(\frac{2}{5}.\frac{1}{x}+\frac{1}{x.2}+\frac{2}{5}=0.5\)

\(\frac{2}{5}.\frac{1}{x}+\frac{1}{2}.\frac{1}{x}+\frac{2}{5}=0.5\)

\(\frac{1}{x}\left(\frac{2}{5}+\frac{1}{2}\right)+\frac{2}{5}=0.5\)

\(\frac{1}{x}.\frac{9}{10}+\frac{2}{5}=0.5\)

\(\frac{1}{x}.\frac{9}{10}=\frac{1}{2}-\frac{2}{5}\)

\(\frac{1}{x}.\frac{9}{10}=\frac{1}{10}\)

\(\frac{1}{x}=\frac{1}{10}:\frac{9}{10}\)

\(\frac{1}{x}=\frac{1}{10}.\frac{10}{9}\)

\(\frac{1}{x}=\frac{1}{9}\)

\(\Rightarrow x=\frac{9.1}{1}=9\)

x^2=16

Suy ra x^2=4^2

Vậy x^2=4^2

[1/(x+2)-1/(x+5)]+[1/(x+5)-1/(x+10)]+[1/(x+10)-1/(x+17)]=x/15.[1/(x+2)-1/(x+17)]
1/(x+2)-1/(x+17)=x/15.[1/(x+2)-1/(x+17)]
1=x/15
x=15

sdsdxc

a: =>7/9:x=1/18-2/9=1/18-4/18=-3/18=-1/6

=>x=-7/9:1/6=-7/9*6=-42/9=-14/3

b: =>x*7/5=2/15+2/5=8/15

=>x=8/15:7/5=8/21

c: =>x-1/2=3/14:4/7=3/8

=>x=3/8+4/8=7/8

d: =>0,4x+0,3x-0,2x=0,7

=>0,5x=0,7

=>x=1,4

7/10

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