1: x=3/4-1/2=3/4-2/4=1/4

2: x-1/5=2/11

=>x=2/11+1/5=21/55

3: x-5/6=16/42-8/56

=>x-5/6=8/21-4/28=5/21

=>x=5/21+5/6=15/14

4: x/5=5/6-19/30

=>x/5=25/30-19/30=6/30=1/5

=>x=1

5: =>|x|=1/3+1/4=7/12

=>x=7/12 hoặc x=-7/12

6: x=-1/2+3/4

=>x=3/4-1/2=1/4

11: x-(-6/12)=9/48

=>x+1/2=3/16

=>x=3/16-1/2=-5/16

1)x= 1/4

2)x= 2/11+ 1/5

   x= 21/55

3)x - 5/6 = 5/21

   x         = 5/21+5/6

   x         = 15/14

4)x/5 = 5/6 + -19/30

   x:5 = 1/5

   x    = 1/5.5

   x    = 1

5) |x| - 1/4 = 6/18

    |x|           = 6/18 - 1/4

    |x|            =7/12

⇒x= 7/12 hoặc -7/12

6)x = -1/2 +3/4

   x= 1/4

7) x/15 = 3/5 + -2/3

   x:15  = -1/15

  x        = -1/15. 15

  x        = -1

8)11/8 + 13/6 = 85/x  

       85/24      = 85/x

  ⇒      x           = 24

9) x - 7/8 = 13/12

   x          = 13/12 + 7/8

   x          = 47/24

10)x - -6/15 = 4/27  

     x            = 4/27 + (-6/15)

    x             = -34/135

11) -(-6/12)+x = 9/48

                    x= 9/48 - 6/12

                    x = -5/16

12) x - 4/6 = 5/25 + -7/15

      x -4/6  =  -4/15

     x           = -4/15 + 4/6

    x             = 2/5

3/2+5/4+9/8/+17/16+33/32-6+x-1/x+1=31/32-2/2015

=(1+1/2)+(1+1/4)+(1+1/8)+(1+1/16)+(1+1/32-6+x-1/x+1=31/32-2/2015

=(1/2+1/4+1/8+1/16+1/32)+(1+1+1+1+1)-6+x-1/x+1=31/32-2/2015

=31/32+5-6+x-1/x+1=31/32-2/2015

=5-6+x-1/x+1=31/32-2/2015-31/32

=-1+x-1/x+1=-2/2015

=x-1/x+1=-2/2015- -1

=x-1/x+1=2013/2015

=>x=2014

ĐKXĐ: x khác 0 

1/(1 ×2)+  1/(2 ×3)+  1/(3 ×4 )+⋯.+  1/(x ×( x+1))=  30/31

1 - 1/2 + 1/2 - 1/3 + 1/3 - 1/4 + ... + 1/x - 1/x +1 = 30/31

1 - 1/x+1 = 30/31

x+1-1/x+1 = 30/31

x/x+1 = 30/31

31x = 30x + 30

31x - 30x = 30

x = 30(TM)

Vậy x là 30.

Giải chi tiết cho mình nha

\(\dfrac{2}{5}+\dfrac{11}{15}=\dfrac{6}{15}+\dfrac{11}{15}=\dfrac{17}{15}\)

\(\dfrac{7}{8}-\dfrac{7}{9}=\dfrac{63}{72}-\dfrac{56}{72}=\dfrac{7}{72}\)

\(\dfrac{11}{13}\times\dfrac{26}{31}=\dfrac{22}{31}\)

\(\dfrac{16}{24}:4=\dfrac{16}{24}\times\dfrac{1}{4}=\dfrac{4}{24}=\dfrac{1}{6}\)

\(30:\dfrac{6}{5}=30\times\dfrac{5}{6}=25\)

\(\dfrac{9}{16}:4=\dfrac{9}{16}\times\dfrac{1}{4}=\dfrac{9}{64}\)

\(\dfrac{1}{2}:\dfrac{1}{3}\times\dfrac{8}{15}=\dfrac{1}{2}\times3\times\dfrac{8}{15}=\dfrac{4}{5}\)

2/5 + 11/15 = 17/15
7/8 - 7/9 = 7/72
11/13 x 26/31 = 22/31
16/24 : 4 = 1/6
30 : 6/5 = 25
9/16 : 4 = 9/64
1/2 : 1/3 x 8/15 = 3/2 x 8/15 = 4/5

\(\frac{1}{4}.\frac{2}{6}.\frac{3}{8}....\frac{30}{62}.\frac{31}{16}=\frac{1.2.3...30.31}{2.3.4....30.31.2^{30}.16}=\frac{1}{2^{30}.2^4}=\frac{1}{2^{34}}=\frac{1}{4^{17}}=\frac{1}{4^x}\)

=> x=17

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

\(a,30+X=120:5+27\\ 30+X=24+27\\ 30+X=51\\ X=51-30=21\\ ---\\ b,40-3\times X=13\\ 3\times X=40-13=27\\ X=\dfrac{27}{3}=9\\ ---\\ 2\times X-8=16\\ 2\times X=16+8\\ 2\times X=24\\ X=\dfrac{24}{2}=12\\ \\---\\ \dfrac{1}{2}\times X-\dfrac{1}{3}=\dfrac{1}{4}\\ \dfrac{1}{2}\times X=\dfrac{1}{4}+\dfrac{1}{3}=\dfrac{7}{12}\\ X=\dfrac{7}{12}:\dfrac{1}{2}=\dfrac{7}{6}\)

a.30+X=24+27

30+X=51

      X=51-30

       X=21

b.3xX=40-13

3xX=27

   X=27:3=9

C.2xX=16+8

2xX=24

 X=24:2=12

D.1/2xX=1/3+1/4

1/2xX=7/12

     X=7/12:1/2=7/6

a) \(30+x=120:5+27\)

\(30+x=24+27\)

\(30+x=51\)

\(x=51-30\)

\(x=21\)

_____

b) \(40-3\times x=13\)

\(3\times x=40-13\)

\(3\times x=27\)

\(x=27:3\)

\(x=9\)

______

c) \(2\times x-8=16\)

\(2\times x=16+8\)

\(2\times x=24\)

\(x=24:2\)

\(x=12\)

______

d) \(\dfrac{1}{2}\times x-\dfrac{1}{3}=\dfrac{1}{4}\)

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

\(\dfrac{1}{2}\times x=\dfrac{7}{12}\)

\(x=\dfrac{7}{12}:\dfrac{1}{2}=\dfrac{7}{12}\times2\)

\(x=\dfrac{7}{6}\)