a(3/15-x)*1/3=2/5 b 3/5*x-1/3=1/4 c 1/4+3/4:x=-2 d 3/4+2(2x-2/3)=2

a) ( $\frac{3}{15}$ - x ) . $\frac{2}{5}$ =$\frac{2}{5}$ 

    $\frac{3}{15}$ - x   =$\frac{2}{5}$ : $\frac{2}{5}$

    $\frac{3}{15}$ - x   =$\frac{2}{5}$ . $\frac{5}{2}$

    $\frac{3}{15}$ - x   = 1

    x = $\frac{3}{15}$ - 1

    x = $\frac{-4}{5}$

Vậy x = x = $\frac{-4}{5}$

b) $\frac{3}{5}$ . x - $\frac{1}{3}$ = $\frac{1}{4}$ 

    $\frac{3}{5}$ . x = $\frac{1}{4}$ + $\frac{1}{3}$ 

    $\frac{3}{5}$ . x = $\frac{3}{12}$ + $\frac{4}{12}$ 

    $\frac{3}{5}$ . x = $\frac{7}{12}$

    x = $\frac{7}{12}$ : $\frac{3}{5}$

    x = $\frac{7}{12}$ . $\frac{5}{3}$

    x = $\frac{35}{36}$

Vậy x = $\frac{35}{36}$

c ) $\frac{1}{4}$ + $\frac{3}{4}$ : x = -2

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

     $\frac{3}{4}$ : x = $\frac{-8}{4}$ - $\frac{1}{4}$

     $\frac{3}{4}$ : x = $\frac{-9}{4}$

     x = $\frac{3}{4}$ : $\frac{-9}{4}$

     x = $\frac{3}{4}$ . $\frac{4}{-9}$

     x = $\frac{1}{-3}$

Vậy x = $\frac{1}{-3}$

d) $\frac{3}{4}$ + 2(2x - $\frac{2}{3}$ ) = 2

     2(2x - $\frac{2}{3}$ ) = 2 - $\frac{3}{4}$

     2(2x - $\frac{2}{3}$ ) = $\frac{8}{4}$ - $\frac{3}{4}$

     2(2x - $\frac{2}{3}$ ) = $\frac{5}{4}$

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

     2x - $\frac{2}{3}$  = $\frac{5}{4}$ . $\frac{1}{2}$

     2x - $\frac{2}{3}$  = $\frac{5}{8}$

     2x = $\frac{5}{8}$ + $\frac{2}{3}$

     2x = $\frac{15}{24}$ + $\frac{16}{24}$

     2x = $\frac{31}{24}$

     x = $\frac{31}{24}$ : 2

     x = $\frac{31}{48}$

Vậy x = $\frac{31}{48}$

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