a. $\dfrac{14}{15}+\dfrac{2}{11}+\dfrac{1}{15}+\dfrac{4}{11}+\dfrac{10}{22}$

$=(\dfrac{14}{15}+dfrac{1}{15})+(\dfrac{2}{11}+\dfrac{4}{11}+\dfrac{10}{22})$

$=1+1=2$

b. $74\times43-43+27\times43$

$=(74-1+27)\times43$

$=100\times43=4300$

\(a)\dfrac{14}{15}+\dfrac{2}{11}+\dfrac{1}{15}+\dfrac{4}{11}+\dfrac{10}{22}\)

\(=\left(\dfrac{14}{15}+\dfrac{1}{15}\right)+\dfrac{2}{11}+\dfrac{4}{11}+\dfrac{5}{11}\)

\(=1+1=2\)

\(b)74\times43-43+27\times43\)

\(=43\times\left(74-1+27\right)\)

\(=43\times100=4300\)

a) x-(-25+x)=13-x

⇒ x+25-x=13-x

⇒ 13-x=25

⇒ x= -12

b) 15-(30+x)=x-(27-l-8l)

⇒ 15-30-x=x-(27-8)

⇒ -15-x=x-19

⇒ -x-x=-19+15

⇒ -2x+4=0

⇒ -2x=-4

⇒ x=2

c) (12x-4³).8³=4.8⁴

⇒ 12x.8³-4³.8³=4.8⁴

⇒ 6144x-32768=16384

⇒ 6144x=49152

⇒ x=8

a: Ta có: \(x-\left(-25+x\right)=13-x\)

\(\Leftrightarrow13-x=25\)

hay x=-12

b: Ta có: \(15-\left(30+x\right)=x-\left(27-\left|-8\right|\right)\)

\(\Leftrightarrow-15-x=x-19\)

\(\Leftrightarrow-2x=-4\)

hay x=2

c: Ta có: \(\left(12x-4^3\right)\cdot8^3=4\cdot8^4\)

\(\Leftrightarrow\left(12x-64\right)\cdot512=16384\)

\(\Leftrightarrow12x-64=32\)

hay x=8

a) \(x+5=20-\left(12-7\right)\)

\(\Rightarrow x+5=20-5\)

\(\Rightarrow x+5=15\)

\(\Rightarrow x=15-5\)

\(\Rightarrow x=10\)

b) \(15-\left(3+2x\right)=2^2\)

\(\Rightarrow3+2x=15-4\)

\(\Rightarrow3+2x=11\)

\(\Rightarrow2x=11-3\)

\(\Rightarrow2x=8\)

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

\(\Rightarrow x=4\)

c) \(-11-\left(19-x\right)=50\)

\(\Rightarrow19-x=-11-50\)

\(\Rightarrow19-x=-61\)

\(\Rightarrow x=61+19\)

\(\Rightarrow x=80\)

d) \(159-\left(25-x\right)=43\)

\(\Rightarrow25-x=159-43\)

\(\Rightarrow25-x=116\)

\(\Rightarrow x=25-116\)

\(\Rightarrow x=-91\)

e) \(\left(79-x\right)-43=-\left(17-52\right)\)

\(\Rightarrow\left(79-x\right)-43=52-17\)

\(\Rightarrow79-x-43=35\)

\(\Rightarrow36-x=35\)

\(\Rightarrow x=1\)

f) \(\left(7+x\right)-\left(21-13\right)=32\)

\(\Rightarrow7+x-8=32\)

\(\Rightarrow x-1=32\)

\(\Rightarrow x=32+1\)

\(\Rightarrow x=33\)

g) \(-x+20=-15+8+13\)

\(\Rightarrow-x+20=6\)

\(\Rightarrow x=20-6\)

\(\Rightarrow x=14\)

h) \(-\left(-x+13-142\right)+18=55\)

\(\Rightarrow x-13+142+18=55\)

\(\Rightarrow x+147=55\)

\(\Rightarrow x=55-147\)

\(\Rightarrow x=-92\)

\(2x+1+\frac{1}{6}+1+\frac{1}{12}+..+1+\frac{1}{90}=10\)

=> 2x + 8 + \(\frac{1}{2.3}+\frac{1}{3.4}+...+\frac{1}{9.10}=10\)

=> 2x + \(\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+...+\frac{1}{9}-\frac{1}{10}=10-8\)

\(2x+1-\frac{1}{10}=2\)

=> 2x + \(\frac{9}{10}=2\)

=> 2x          = 2 - 9/10

=>2x           = 11/10 

=> x              = 11/10 : 2

x                  =  11/20 

thang Tran ơi,2x+1-1/10 ở đâu vậy

Phải là 2x+1/2-1/10 chứ

  a)  ( 15 x 13 - 21 ) : 2 +108

=(195-21):2+108

=174:2+108

=195

b) (548x13+1096)x43:15:86

=(7124+1096)x43:15:86

=8220x43:15:86

=353460:15:86

=274

a,x+(-45)=(-62)+17

<=>x=(-62)+17+45

<=>x=0

b,x+29=\(|-43|\)-+(-43)

<=>x=43-43-29

<=>x=-29

c,43+(9-21)=317-(x+317)

<=>31=317-x-317

<=>31=-x

<=>-31=x

d, (15-x)+(x-12)=7-(-5-x)

<=>15-x+x-12=7+5+x

<=>3=12+x

<=>-9=x

e, x-{57-[42+(-23-x)]}=13-{47+[25-(32-x)]}

<=>x-57+42-23-x=13-47-25+32-x

<=>76=-27-x

<=>103=-x

<=>-103=x

f,\(|x|+|-4|=7\)

<=>\(|x|\)+4=7

<=>\(|x|\)=3

<=>x=3 hoặc x=-3

a.  x + (-45) = (-62 ) + 17

b.  x + 29 = /-43/ + (-43)

c.  43 + (9 - 21) = 317 - ( x +317)

d.  (15 - x ) + ( x - 12 ) = 7 - ( -5 + x )

e.  x - { 57 - [ 42 + ( -23 - x ) ] } = 13 - { 47 + [ 25 - ( 32 - x ) ] }

Tính nhanh 

a) 43 x 64 + 43 x 36

= 43 x (64 + 36)

= 43 x 100

= 4300

b) 26  + 27 + 28 + 29 + ... + 33 ( Có 8 số hạng )

= (33 + 26) x 8 : 2 = 236

c) 135 + 36 + 65 + 40

= (135 + 65) + (36 + 40)

= 200 + 76

= 276

d) 463 + 318 + 137 + 22

= (463 + 137) + ( 318 + 22 )

= 600 + 340

= 940

đ ) 20 + 21 + ... + 30 ( có 11 số hạng )

= ( 30 + 20 ) x 11 : 2 = 275