a: =(-20/23-3/23)+(2/3+2/5+7/15)

=-1+10/15+6/15+7/15

=23/15-1=8/15

b: \(=\dfrac{7}{5}\cdot\dfrac{29}{4}-\dfrac{7}{5}\cdot\dfrac{9}{4}+\dfrac{41}{13}=\dfrac{7}{5}\cdot5+\dfrac{41}{13}=7+\dfrac{41}{13}=\dfrac{132}{13}\)

c: =3,07+7,005-23,005+5,23

=8,3-16

=-7,7

AI GIÚP EM VỚI Ạ

\(#N\)

\(-\dfrac{11}{7}+\dfrac{13}{-2}+-\dfrac{6}{17}=-\dfrac{113}{14}+-\dfrac{6}{17}=-\dfrac{2005}{238}\)

\(\dfrac{13}{-8}+-\dfrac{7}{20}+\dfrac{3}{-8}=\left(-\dfrac{13}{8}+-\dfrac{3}{8}\right)+-\dfrac{7}{20}=-2+-\dfrac{7}{20}=-\dfrac{47}{20}\)

\(-\dfrac{4}{7}+\dfrac{11}{5}+\dfrac{1}{5}+-\dfrac{7}{3}=-\dfrac{4}{7}+\left(\dfrac{11}{5}+\dfrac{1}{5}\right)+-\dfrac{7}{3}=-\dfrac{4}{7}+\dfrac{12}{5}+-\dfrac{7}{3}=-\dfrac{53}{105}\)

\(-\dfrac{2}{5}.\dfrac{4}{7}+\dfrac{-3}{5}.\dfrac{2}{7}+\dfrac{-3}{5}\)

= \(\dfrac{-8}{35}+\dfrac{-6}{35}+\dfrac{-3}{5}\) 

=\(\dfrac{-8-6-21}{35}\) 

=\(\dfrac{-35}{35}\) 

=-1

`(-2)/5.4/7+(-3)/5.2/7+(-3)/5`

`=(-8)/3 +(-6)/35+(-3)/5`

`=(-8)-6-21/35`

`=(-35)/35`

`=(-1)`

`@Nae`

(-2)/5 x 4/7 + (-3)/5 x 2/7 + (-3)/5

`=(-8)/3 +(-6)/35+(-3)/5`

`=(-8)-6-21/35`

`=(-35)/35`

`=(-1)`

`@Nae`

\(\frac{2}{5.7}+\frac{5}{7.12}+\frac{8}{12.20}+\frac{3}{140}\)

\(=\frac{1}{5}-\frac{1}{7}+\frac{1}{7}-\frac{1}{12}+\frac{1}{12}-\frac{1}{20}+\frac{3}{140}\)

\(=\frac{1}{5}-\frac{1}{20}+\frac{3}{140}\)

\(=\frac{3}{20}+\frac{3}{140}\)

\(=\frac{6}{35}\)

(1/2-2/3)-(5/3-3/2)+(7/3-5/2)

=1/2-2/3-5/3+3/2+7/3-5/2

=(1/2+3/2-5/2)-(2/3+5/3-7/3)

=-1/2-0=-1/2

5.(-8).2.(-3) = ( 5 . 2 ) . [ -8 . ( -3) ] = 10 . 24 = 240

   5 . ( - 8 ) . 2 . ( - 3 ) 

=  ( 5 . 2 ) . [ - 8 . ( - 3 ) ] 

= 10 . 24 

= 240 

   ( 2020 - 7 + 3 ) - ( 7 + 3 - 2020 ) 

= 2020 - 7 + 3 - 7 - 3 + 2020 

= ( 2020 + 2020 ) + ( 3 - 3 ) - ( 7 + 7 ) 

= 4040 + 0 - 14 

= 4026 

   4.( - 5 )² + 2. ( - 5 ) - 20 

= 4. ( - 5 ) . ( - 5 ) + 2 . ( - 5 ) - 20 

= ( - 5 ) . [ 4 . ( - 5 ) + 2 ] - 20 

= ( - 5 ) . ( - 18 ) - 20 

= 90 - 20 = 70 

5(-8).2.(-3)=(5.2).[(-8).(-3)]=10.24=240

(2020-7+3)-(7+3-2020)=2020-7+3 - 7-3+2020=(2020+2020)+(3-3)-(7+7)=4040+0-16=4026

4(-5)²+2(-5)-20=4.(-5).(-5)+2(-5)-20=(-5).[4.(-5)+2]-20=(-5).(-18)-20=90-20=70

Bài 1: 

\(A=\dfrac{-1}{3}+1+\dfrac{1}{3}=1\)

\(B=\dfrac{2}{15}+\dfrac{5}{9}-\dfrac{6}{9}=\dfrac{2}{15}-\dfrac{1}{9}=\dfrac{18-15}{135}=\dfrac{3}{135}=\dfrac{1}{45}\)

\(C=\dfrac{-1}{5}+\dfrac{1}{4}-\dfrac{3}{4}=\dfrac{-1}{5}-\dfrac{1}{2}=\dfrac{-7}{10}\)

Bài 2: 

a: \(=\dfrac{1}{5}+\dfrac{1}{2}+\dfrac{2}{5}-\dfrac{3}{5}+\dfrac{2}{21}-\dfrac{10}{21}+\dfrac{3}{20}\)

\(=\left(\dfrac{1}{5}+\dfrac{2}{5}-\dfrac{3}{5}\right)+\left(\dfrac{2}{21}-\dfrac{10}{21}\right)+\left(\dfrac{1}{2}+\dfrac{3}{20}\right)\)

\(=\dfrac{-8}{21}+\dfrac{13}{20}=\dfrac{113}{420}\)

b: \(B=\dfrac{21}{23}-\dfrac{21}{23}+\dfrac{125}{93}-\dfrac{125}{143}=\dfrac{6250}{13299}\)

Bài 3:

\(\dfrac{7}{3}-\dfrac{1}{2}-\left(-\dfrac{3}{70}\right)=\dfrac{7}{3}-\dfrac{1}{2}+\dfrac{3}{70}=\dfrac{490}{210}-\dfrac{105}{210}+\dfrac{9}{210}=\dfrac{394}{210}=\dfrac{197}{105}\)

\(\dfrac{5}{12}-\dfrac{3}{-16}+\dfrac{3}{4}=\dfrac{5}{12}+\dfrac{3}{16}+\dfrac{3}{4}=\dfrac{20}{48}+\dfrac{9}{48}+\dfrac{36}{48}=\dfrac{65}{48}\)

Bài 4:

 \(\dfrac{3}{4}-x=1\)

\(\Rightarrow-x=1-\dfrac{3}{4}\)

\(\Rightarrow x=-\dfrac{1}{4}\)

Vậy: \(x=-\dfrac{1}{4}\)

\(x+4=\dfrac{1}{5}\)

\(\Rightarrow x=\dfrac{1}{5}-4\)

\(\Rightarrow x=-\dfrac{19}{5}\)

Vậy: \(x=-\dfrac{19}{5}\)

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

\(\Rightarrow x=2+\dfrac{1}{5}\)

\(\Rightarrow x=\dfrac{11}{5}\)

Vậy: \(x=\dfrac{11}{5}\)

\(x+\dfrac{5}{3}=\dfrac{1}{81}\)

\(\Rightarrow x=\dfrac{1}{81}-\dfrac{5}{3}\)

\(\Rightarrow x=-\dfrac{134}{81}\)

Vậy: \(x=-\dfrac{134}{81}\)

a) 7/3 + 2/5 . 5/6 = 7/3 + 1/3 = 8/3

b) 2/3 - 7/3 : 2 4/5 = 2/3 - 7/3 : 14/5 = 2/3 - 7/3 . 5/14 = 2/3 - 5/6 = 4/6 - 5/6 = -1/6