\(a,\dfrac{3}{8}=\dfrac{6}{x}\\ \Rightarrow x=6:\dfrac{3}{8}\\ \Rightarrow x=16\\ b,\dfrac{1}{9}=\dfrac{x}{27}\\ \Rightarrow x=\dfrac{1}{9}.27\\ \Rightarrow x=3\\ c,\dfrac{4}{x}=\dfrac{8}{6}\\ \Rightarrow x=4:\dfrac{4}{3}\\ \Rightarrow x=3\\ d,\dfrac{3}{x-5}=\dfrac{-4}{x+2}\\ \Rightarrow3\left(x+2\right)=-4\left(x-5\right)\\ \Rightarrow3x+6=-4x+20\\ \Rightarrow3x+6+4x-20=0\\ \Rightarrow7x-14=0\\ \Rightarrow7x=14\\ \Rightarrow x=2\)

a: =>6/x=3/8

hay x=16

b: =>x/27=1/9

nên x=3

c: =>4/x=4/3

nên x=3

d: =>3/x-5=-4/x+2

=>3x+2=-4x+20

=>7x=18

hay x=18/7

Ta có : ( x+1 ) + ( x + 2 ) + ( x + 3 ) + ( x + 4 ) + ( x + 5 ) = 30

            ( x + x + x +x +x ) + ( 1 + 2 + 3 + 4 + 5 ) = 30

             x * 5 + 15 = 30

              x * 5 = 30 - 15

              x * 5 = 15

                   x = 15 : 5 

                  x = 3

Vậy x = 3

Duyệt đi , chúc bạn học giỏi

(x + 1) + (x + 2) + (x + 3) + (x + 4) + (x + 5) = 4 + 5 + 6 + 7 + 8

x + 1 + x + 2 + x + 3 + x + 4 + x + 5 = 30

\(x\)x 5  + 15 = 30

\(x\)x 5 = 30 - 15 = 15

x = 15 : 5 = 3

A

\(\frac{3}{5}\div\frac{4}{5}+\frac{1}{2}\times\frac{2}{3}\)

\(=\frac{3}{4}+\frac{1}{3}\)

\(=\frac{13}{12}\)

B

\(\frac{5}{4}\times x=\frac{3}{8}+\frac{1}{4}\)

 \(\frac{5}{4}\times x =\frac{5}{8}\)

\(x=\frac{5}{8}\div\frac{5}{4}\)

\(x=\frac{4}{8}=\frac{1}{2}\)

AI TRA LOI GIUP MINK DI

\(x+\dfrac{3}{4}=\dfrac{1}{2}+\dfrac{9}{8}\\ x+\dfrac{3}{4}=\dfrac{4}{8}+\dfrac{9}{8}\\ x+\dfrac{3}{4}=\dfrac{13}{8}\\ x=\dfrac{13}{8}-\dfrac{3}{4}\\ x=\dfrac{13}{8}-\dfrac{6}{8}\\ x=\dfrac{7}{8}\)

x + 3/4 = 1/2 + 9/8

x + 3/4 = 13/8

      x    = 13/8 -3/4

      x    = 7/8

x(3-x)=0

Th1: x=0

Th2: 3-x=0     =>       x=3

Vậy x=0 và x=3

(x+2)(4x-8)=0

Th1: x+2= 0        =>         x=-2

Th2: 4x-8 =0           =>             4x =8

                                                x= 2

Vậy x= +- 2 (cộng trừ 2 nhé)

(x+1)+(x+2)+(x+3)+....+(x+199)=5750

199x +(1+2+3+...199) =5750

199x+ {(199+1)* [(199-1)+1] : 2} =5750

199x + 19900= 5750

199x = -14150

x= -14150/199

12x/6 + 4x/6 - 3x/6 = 3/8 - 1/4 - 1/6

13x/6 = (9 - 6 - 4)/24 = -1/24

--> x = -1/52

\(\dfrac{3}{x-5}=\dfrac{-4}{x+2}\)=>3.(x+2)=(x-5).(-4)

=> 3.2+3.x=x.(-4)-(-4).5

=>6+3.x=x.(-4)-(-20)

=>3.x-x.(-4)=20-6

=>3.x-x.(-4)=14

=>x.(3+4)=14(vì 3-(-4)=3+4)

=>x.7=14

=>x=14:7

=>x=2

\(\dfrac{3}{8}=\dfrac{6}{x}\) =>3.x=6.8

3.x=48

x=48:3

x=16

mấy ý sau làm tương tự nhé

ta có:x/2+3x/4+x/2+x/4=8

=>(x/2+x/2)+(3x/4+x/4)=8

=>x+x=8

=>2x=8

=>x=4

kích mình nhé