a:  =-5/6-3/7=-35/42-18/42=-53/42

b: =18/45-20/45=-2/45

c: =-24/35

d: =2/3x-5/4=-10/12=-5/6

\(\dfrac{-5}{6}+\dfrac{3}{7}=\dfrac{-5\times7+3\times6}{6\times7}=\dfrac{-17}{42}.\)

\(\dfrac{2}{5}-\dfrac{4}{9}=\dfrac{2\times9-4\times5}{5\times9}=\dfrac{-2}{45}.\)

\(\dfrac{-6}{5}\times\dfrac{4}{7}=\dfrac{-6\times4}{5\times7}=\dfrac{-24}{35}.\)

\(\dfrac{2}{3}:\dfrac{-4}{5}=\dfrac{2}{3}\times\dfrac{5}{-4}=\dfrac{-5}{6}.\)

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

\(\left(\dfrac{1}{2}+\dfrac{1}{3}\right)\times\dfrac{2}{5}=\dfrac{5}{6}\times\dfrac{2}{5}=\dfrac{2}{6}=\dfrac{1}{3}\)

\(\left(\dfrac{1}{2}+\dfrac{1}{3}\right)\times\dfrac{2}{5}=\left(\dfrac{3}{6}+\dfrac{2}{6}\right)\times\dfrac{2}{5}=\dfrac{5}{6}\times\dfrac{2}{5}=\dfrac{1}{3}\times\dfrac{1}{1}=\dfrac{1}{3}\)

( x - 1/2 ) : 3/11 =11/4

 x - 1/2  = 11/4 x 3/11

 x - 1/2  = 3/4

         x = 3/4 + 1/2

         x = 5/4

Vậy x = 5/4

(2x + 3/8 ) . 7/4 =-21/32

2x + 3/8 = -21/32 : 7/4

2x + 3/8 = -3/8

         2x = -3/8 - 3/8

         2x = -3/4

           x = -3/4 : 2

           x = -3/8

Vậy x = -3/8

x - x/3 = 3/57 : 12/19

<=> x - x/3 = 1/19

<=> 2x/3 = 1/19

<=> 2X x 19 = 1 x 3

<=> 2X x 19 = 3

<=> 2x = 3/19

<=> x = 3/38

Vậy x = 3/38

a: k=-6

b: y=-6x