a).$\frac{2}{5}$ + $\frac{3}{4}$ : x = $\frac{-1}{2}$ 

$\frac{3}{4}$ : x = $\frac{-1}{2}$ - $\frac{2}{5}$ 
$\frac{3}{4}$ : x = $\frac{-9}{10}$  
x = $\frac{3}{4}$ : $\frac{-9}{10}$
x = $\frac{-5}{6}$
Vậy x = $\frac{-5}{6}$
b). $\frac{5}{7}$ - $\frac{-2}{3}$ . x = $\frac{4}{5}$
$\frac{-2}{3}$ . x = $\frac{5}{7}$ - $\frac{4}{5}$
$\frac{-2}{3}$ . x = $\frac{-3}{35}$ 
x = $\frac{-3}{35}$ : $\frac{2}{3}$
x = $\frac{-9}{70}$
Vậy x = $\frac{-9}{70}$
c). $\frac{1}{2}$.x + $\frac{3}{5}$.x = $\frac{-2}{3}$
x.($\frac{1}{2}$.x + $\frac{3}{5}$) = $\frac{-2}{3}$
x.$\frac{11}{10}$ = $\frac{-2}{3}$
x = $\frac{-2}{3}$ : $\frac{11}{10}$ 
x = $\frac{-20}{33}$ 
Vậy x = $\frac{-20}{33}$ 
d).$\frac{4}{7}$.x - x = $\frac{-9}{14}$ 
x.($\frac{4}{7}$ - 1) = $\frac{-9}{14}$
x.($\frac{-3}{7}$) = $\frac{-9}{14}$
x = $\frac{-9}{14}$ : ($\frac{-3}{7}$)
x = $\frac{3}{2}$
Vậy x = $\frac{3}{2}$
Gửi ặ :)
#TN__My

a) `\frac{2}{5} +` `\frac{3}{4} : x` = `\frac{-1}{2}`

`\frac{3}{4} : x = `  `\frac{-1}{2}` - `\frac{2}{5}`

`\frac{3}{4} : x = ` `\frac{-9}{10}`

`x = ` `\frac{3}{4} :` `\frac{-9}{10}` 

`x = ` `\frac{-5}{6}`

 b) `\frac{5}{7} -` `\frac{2}{3} . x =` `\frac{4}{5}`

  `\frac{2}{3} . x = ` `\frac{-3}{35}`

 ` x =` `\frac{-3}{35} : ` `\frac{2}{3}`

  `x =` `\frac{-9}{70}`

c) `\frac{1}{2} x +` `\frac{3}{5} x =` `\frac{-2}{3}`

`x .` `(\frac{1}{2} +` `\frac{3}{5}) =``\frac{-2}{3}`

`x .` `\frac{11}{10} =` `\frac{-2}{3}`

`x = ` `\frac{-2}{3} :` `\frac{11}{10}` 

`x = ` `\frac{-20}{33}`

d) `\frac{4}{7}x - x =` `\frac{-9}{14}`

`\frac{4}{7}x - x . 1 =` `\frac{-9}{14}`

`x . ( \frac{4}{7} - 1) = ` `\frac{-9}{14}`

`x . \frac{-3}{7} = `  `\frac{-9}{14}`

`x =` `\frac{-9}{14} :` `\frac{-3}{7}`

`x = ` `\frac{3}{2}`