\(a,\dfrac{2}{3}.x=\dfrac{2}{7}\\ x=\dfrac{2}{7}:\dfrac{2}{3}=\dfrac{3}{7}\\ ---\\ b,x.\dfrac{3}{5}=\dfrac{2}{5}\\ x=\dfrac{2}{5}:\dfrac{3}{5}=\dfrac{2}{3}\\ ---\\ c,x:\dfrac{8}{13}=\dfrac{13}{7}\\x=\dfrac{13}{7}.\dfrac{8}{13}=\dfrac{8}{7}\\ ----\\ d,\dfrac{3}{2}:x=\dfrac{7}{4}\\ x=\dfrac{3}{2}:\dfrac{7}{4}=\dfrac{3}{2}.\dfrac{4}{7}=\dfrac{6}{7}\)

3x + 4x + 8x - 2( 32 + 8 ) = 30

15x - 2.40 = 30

15x - 80 = 30

15x = 30 + 80

15x = 110

x = 110 : 15

x = 22/3

3x+4x+8x - 2.(32+8) = 30

( 3 + 4 + 8 )x - 2.40 = 30

15x - 80= 30

15x  = 30 + 80 = 110 

x = 110 : 15 = \(\frac{22}{3}\)

\(a,30+X=120:5+27\\ 30+X=24+27\\ 30+X=51\\ X=51-30=21\\ ---\\ b,40-3\times X=13\\ 3\times X=40-13=27\\ X=\dfrac{27}{3}=9\\ ---\\ 2\times X-8=16\\ 2\times X=16+8\\ 2\times X=24\\ X=\dfrac{24}{2}=12\\ \\---\\ \dfrac{1}{2}\times X-\dfrac{1}{3}=\dfrac{1}{4}\\ \dfrac{1}{2}\times X=\dfrac{1}{4}+\dfrac{1}{3}=\dfrac{7}{12}\\ X=\dfrac{7}{12}:\dfrac{1}{2}=\dfrac{7}{6}\)

a.30+X=24+27

30+X=51

      X=51-30

       X=21

b.3xX=40-13

3xX=27

   X=27:3=9

C.2xX=16+8

2xX=24

 X=24:2=12

D.1/2xX=1/3+1/4

1/2xX=7/12

     X=7/12:1/2=7/6

a) \(30+x=120:5+27\)

\(30+x=24+27\)

\(30+x=51\)

\(x=51-30\)

\(x=21\)

_____

b) \(40-3\times x=13\)

\(3\times x=40-13\)

\(3\times x=27\)

\(x=27:3\)

\(x=9\)

______

c) \(2\times x-8=16\)

\(2\times x=16+8\)

\(2\times x=24\)

\(x=24:2\)

\(x=12\)

______

d) \(\dfrac{1}{2}\times x-\dfrac{1}{3}=\dfrac{1}{4}\)

\(\dfrac{1}{2}\times x=\dfrac{1}{4}+\dfrac{1}{3}\)

\(\dfrac{1}{2}\times x=\dfrac{7}{12}\)

\(x=\dfrac{7}{12}:\dfrac{1}{2}=\dfrac{7}{12}\times2\)

\(x=\dfrac{7}{6}\)

c)\(\dfrac{3}{8}\times\dfrac{5}{8}+y=\dfrac{5}{4}\) 

   \(\dfrac{15}{64}+y=\dfrac{5}{4}\) 

           \(y=\dfrac{5}{4}-\dfrac{15}{64}\) 

           \(y=\dfrac{65}{64}\)

d, \(\dfrac{3}{8}+\dfrac{5}{8}\times y=\dfrac{5}{4}\) 

          \(\dfrac{5}{8}\times y=\dfrac{5}{4}-\dfrac{3}{8}\) 

          \(\dfrac{5}{8}\times y=\dfrac{7}{8}\) 

                 \(y=\dfrac{7}{8}:\dfrac{5}{8}\) 

                \(y=\dfrac{7}{5}\)

a) 3/4 x y = 9/10

y = 9/10 : 3/4

y = 6/5

b) 3/5 : y = 7/20

y = 3/5 : 7/20 

y = 12/7

e)\(\dfrac{1}{3}+\dfrac{2}{3}:x=\dfrac{5}{2}\) 

       \(\dfrac{2}{3}:x=\dfrac{5}{2}-\dfrac{1}{3}\) 

       \(\dfrac{2}{3}:x=\dfrac{13}{6}\) 

             \(x=\dfrac{2}{3}:\dfrac{13}{6}\) 

             \(x=\dfrac{4}{13}\)

a) x . ( y + 3 ) = -8

Vì x;y là số nguyên => x và y+3 là số nguyên

                                 => x và y+3 thuộc Ư(-8)

Vậy............................................

a) x . ( y + 3 ) = -8

 ta phân tích : -8 = 2 . -4  = -2 . 4 

                           = -8 . 1 = -1 . 8

ta có :

x = 2 thì y + 3 = -4 => y = -7

x =4 thì y  + 3 = -2 => y = -5

x = -2 thì y +3 = 4 => y = 1

x = -4 thì y + 3 = 2 => y = 5

x = -8 thì y +3 = 1 => y = -2

x = 8 thì y + 3 = -1 => y = -4

x = 1 thì y + 3 = -8 => y = -11

x = -1 thì y + 3 = 8 => y = 5

vậy x = { -2;2;4;-4;1;-1;8;-8 }

      y = { -7;-5;5;1;-2;-4;-11 }

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