a: \(=\dfrac{-5}{8}+\dfrac{7}{12}=\dfrac{-15}{24}+\dfrac{14}{24}=\dfrac{-1}{24}\)

b: \(=\dfrac{3}{4}-\dfrac{5}{6}+\dfrac{11}{12}=\dfrac{9}{12}-\dfrac{10}{12}+\dfrac{11}{12}=\dfrac{10}{12}=\dfrac{5}{6}\)

c: \(=\dfrac{6}{36}-\dfrac{1}{36}=\dfrac{5}{36}\)

d: \(=\dfrac{5}{12}+\dfrac{5}{12}=\dfrac{10}{12}=\dfrac{5}{6}\)

e: \(=\dfrac{-8}{56}-\dfrac{7}{56}=\dfrac{-15}{56}\)

f: \(=\dfrac{-5}{15}+\dfrac{3}{25}=\dfrac{-25}{75}+\dfrac{9}{75}=\dfrac{-16}{75}\)

  \(\dfrac{1}{2}+\dfrac{3}{4}-\left(\dfrac{3}{4}-\dfrac{4}{5}\right)\)

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

=\(\left(\dfrac{1}{2}+\dfrac{4}{5}\right)+\left(\dfrac{3}{4}-\dfrac{3}{4}\right)\) 

=\(\left(\dfrac{5}{10}+\dfrac{8}{10}\right)+0\)

=\(\dfrac{13}{10}\)

\(-\dfrac{7}{25}.\dfrac{11}{13}+\left(-\dfrac{7}{25}\right).\dfrac{2}{13}-\dfrac{18}{25}\)

=\(-\dfrac{7}{25}.\cdot\left(\dfrac{11}{13}+\dfrac{2}{13}\right)-\dfrac{18}{25}\) 

=\(-\dfrac{7}{25}.1-\dfrac{18}{25}\) 

=\(-\dfrac{7}{25}-\dfrac{18}{25}\) 

=\(-\dfrac{25}{25}\) = \(-1\)

(-3,2) +\(\dfrac{15}{64}+\left(0.8-2\dfrac{4}{15}\right):3\dfrac{2}{3}\) 

=\(-\dfrac{16}{5}+\dfrac{15}{64}+(\dfrac{4}{5}-\dfrac{34}{15}):\dfrac{11}{3}\)

=\(-\dfrac{16}{5}+\dfrac{15}{64}+(-\dfrac{22}{5}):\dfrac{11}{3}\)

=\(-\dfrac{16}{5}+\dfrac{15}{64}+\dfrac{-2}{5}\)

=(\(-\dfrac{16}{5}+\dfrac{-2}{5}\)) +\(\dfrac{15}{64}\)

=\(-\dfrac{18}{5}+\dfrac{15}{64}\)

\(-\dfrac{1152}{320}+\dfrac{75}{320}\)

\(-\dfrac{1077}{320}\)

A = - 2 / 5 + ( - 2 / 5 + 2 )

A = - 2 / 5 + 8 / 5

A = 6 / 5

B = ( - 5 / 24 + 0, 75 + 7 / 12 ) : - 17/8

B = 9 / 8 : - 17/8

B = -9 / 17

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

C = 3 / 7 - 1 / 5 - 3 / 7 

C = - 1 / 5 

D = ( 6 - 14 / 5 ) . 25 / 8 - 8 / 5 : 1 / 4 

D = 16 / 5 . 25 / 8 - 8 / 5 . 4 

D = 10 - 6 , 4 

D = 3,6

\(A=-\frac{2}{5}+\left[\left(-\frac{2}{5}\right)+2\right]=\left[\left(-\frac{2}{5}\right)+\left(-\frac{2}{5}\right)\right]+2=\left(-\frac{4}{5}\right)+2=\left(-\frac{4}{5}\right)+\frac{10}{5}=\frac{6}{5}\)\(\frac{10}{5}=\frac{6}{5}\)

\(B=\left[\left(-\frac{5}{24}\right)+0,75+\frac{7}{12}\right]:\left(\frac{-17}{8}\right)\)\(=\left[\left(-\frac{5}{24}\right)+\frac{3}{4}+\frac{7}{12}\right].\frac{-8}{17}\)

   \(=\left[\left(-\frac{5}{24}\right)+\frac{18}{24}+\frac{14}{24}\right].\frac{-8}{17}\)\(=\frac{27}{24}.\frac{-8}{17}=\frac{9}{8}.\frac{-8}{17}=\frac{9.\left(-8\right)}{8.17}=\frac{-9}{17}\)

\(C=\frac{3}{7}+\left[\left(-\frac{1}{5}\right)+\left(-\frac{3}{7}\right)\right]=\left[\frac{3}{7}+\left(-\frac{3}{7}\right)\right]+\left(-\frac{1}{5}\right)=-\frac{1}{5}\)

\(D=\left(6-\frac{14}{5}\right).\frac{25}{8}-\frac{8}{5}:\frac{1}{4}=\left(\frac{30}{5}-\frac{14}{5}\right).\frac{25}{8}-\frac{8}{5}.4\)

\(=\frac{16}{5}.\frac{25}{8}-\frac{32}{5}=\frac{16.25}{5.8}-\frac{32}{5}=10-\frac{32}{5}\)\(=\frac{50}{5}-\frac{32}{5}=\frac{18}{5}\)

A) 7/12+5/12 : 6 -11/36

=7/12 + 5/72 -11/36

=47/72-11/36

=25/72

Bài 1:

a: \(x=\dfrac{2}{3}:\dfrac{3}{5}=\dfrac{2}{3}\cdot\dfrac{5}{3}=\dfrac{10}{9}\)

b: \(x=\dfrac{17}{8}:\dfrac{7}{17}=\dfrac{17}{8}\cdot\dfrac{17}{7}=\dfrac{289}{56}\)

c: \(x=-\dfrac{3}{4}:\dfrac{7}{12}=\dfrac{-3}{4}\cdot\dfrac{12}{7}=\dfrac{-63}{28}=-\dfrac{9}{4}\)

d: \(\Leftrightarrow x\cdot\dfrac{1}{6}=\dfrac{3}{8}-\dfrac{1}{4}=\dfrac{1}{4}\)

hay \(x=\dfrac{1}{4}:\dfrac{1}{6}=\dfrac{3}{2}\)

e: \(\Leftrightarrow\dfrac{1}{2}:x=-4-\dfrac{1}{3}=-\dfrac{17}{3}\)

hay \(x=-\dfrac{1}{2}:\dfrac{17}{3}=\dfrac{-3}{34}\)

dad

Dấu ^ là dấu gạch ngang của phản số nhé

a , \(\frac{7}{8}:\frac{1}{6}+\frac{7}{8}.\frac{-7}{18}\)  

  = \(\frac{21}{4}+\frac{-49}{144}=\frac{707}{144}\)

b, -1 : (-5) + \(\frac{1}{15}-\frac{-1}{15}\)

 = \(\frac{1}{5}+0=\frac{1}{5}\)

c, \(\frac{9}{10}-\frac{1}{10.9}-\frac{1}{9.8}-\frac{1}{8.7}-\frac{1}{7.6}-\frac{1}{6.5}-\frac{1}{5.4}-\frac{1}{4.3}-\frac{1}{3.2}-\frac{1}{2.1}\)

 =  \(\frac{9}{10}-\frac{10-9}{10.9}-\frac{9-8}{9.8}-\frac{8-7}{8.7}-\frac{7-6}{7.6}-\frac{6-5}{6.5}-\frac{5-4}{5.4}-\frac{4-3}{4.3}-\frac{3-2}{3.2}.\frac{2-1}{2.1}\)

 = \(\frac{9}{10}-1-\frac{1}{10}-1-\frac{1}{9}-1-\frac{1}{8}-1-\frac{1}{7}-1-\frac{1}{6}-1-\frac{1}{5}-1-\frac{1}{4}-1-\frac{1}{3}-1-\frac{1}{2}\)

 = \(\frac{9}{10}-\left(1+1+1+1+1+1+1+1+1\right)-\left(\frac{1}{10}+\frac{1}{9}+\frac{1}{8}+...+\frac{1}{2}\right)\)

= \(\frac{9}{10}-9-1,928=\frac{9}{10}-7,071=-6.171\)