a, 3/4 + 1/4.x=2

    1/4.x        = 2-3/4

     1/4.x      =5/4

     x           = 5/4:1/4

     x           = 5

b, x-2/3.9/4=2,5-1/2

    x-2/3.9/4=2

    x-2/3     =2:9/4

    x-2/3   =8/9

     x        = 8/9+2/3

     x         = 14/9

c, 2.x+1/3=4/3

    2.x      =4/3-1/3

    2.x      =1

       x      =11:2

       x      = 1/2

=> x + 1/2 = 5/6 + 3/4

=> x + 1/2 = 19/12

=> x = 19/12 - 1/2

=> x = 13/12

Vậy x = 13/12

Tk mk nha

a  X+1/2-3/4=5/6 suy ra :                                                                        Mỉnh phải đi ngủ rồi mai mình giải tiếp cho nhé

  X+1/2=5/6+3/4

  X+1/2=19/12

  X=19/12-1/2

  X=13/12                                                                                            

Bài giải:

a, \(11.xx-66=4.x+11\)

\(11x^2-66=4.x+11\)

\(11x^2-66-4.x-11=0\)

\(11x^2-77-4x=0\)

\(11x^2-4x-77=0\)

\(x=\frac{-\left(-4\right)+\sqrt{\left(-4\right)^2-4.11.\left(-77\right)}}{2.11}\)

\(x=\frac{4+\sqrt{16}+3388}{22}\)

\(x=\frac{4+\sqrt{3404}}{22}\)

\(x=\frac{4+2\sqrt{851}}{22}\)

\(x=\frac{2-\sqrt{851}}{11}\)

\(\Rightarrow\)Có hai trường hợp: \(x_1=\frac{2-\sqrt{851}}{11};x_2=\frac{2+\sqrt{851}}{11}\)

Tớ bận rồi, cậu coi câu trên đã nhé ! Tớ xin lỗi, khi nào tớ sẽ làm tiếp =)) 

dấu trừ đầu tiên các bạn thay thành số 4 hộ mik nhé

\(\left(\frac{3}{4}x\right):\frac{1}{2}=\frac{4}{5}\)

=>\(\frac{3}{4}x=\frac{4}{5}.\frac{1}{2}\)

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

=>\(x=\frac{2}{5}:\frac{3}{4}\)

=>\(x=\frac{8}{15}\)

\(\left(\frac{3}{4}.x\right)=\frac{4}{5}.\frac{1}{2}\)

\(\left(\frac{3}{4}.x\right)=\frac{2}{5}\)

\(\Rightarrow x=\frac{2}{5}:\frac{3}{4}=\frac{8}{15}\)

k nha

\(\left(\frac{3}{4}.x\right):\frac{1}{2}=\frac{4}{5}\)

\(\left(\frac{3}{4}.x\right)=\frac{4}{5}.\frac{1}{2}\)

\(\left(\frac{3}{4}.x\right)=\frac{2}{5}\)

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

\(x=\frac{8}{15}\)

\(x\cdot\frac{1}{2}\cdot\frac{1}{3}=\frac{3}{4}\\ x\cdot\frac{1}{6}=\frac{3}{4}\\ x=\frac{3}{4}:\frac{1}{6}\\ x=\frac{9}{2}\)

Vậy.....

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

\(x=\frac{3}{4}\div\frac{1}{3}\div\frac{1}{2}\)

\(x=\frac{9}{2}\)

\(X\text{ × }\frac{1}{2}\text{ × }\frac{1}{3}=\frac{3}{4}\)

\(X\text{ × }\frac{1}{6}=\frac{3}{4}\)

\(X=\frac{3}{4}:\frac{1}{6}\)

\(X=\frac{9}{2}\)

\(\left(\frac{3}{4}\cdot x\right):\frac{1}{2}=\frac{4}{5}\)

\(\frac{3}{4}\cdot x=\frac{4}{5}\cdot\frac{1}{2}\)

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

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

\(x=\frac{8}{15}\)

2 chữ x hả bạn

(3X x):1/2=4/5

=>3 X x=4/5x1/2

=> 3 X x= 2/5

=> x=2/5:3

=>x=2/15

\(\frac{1}{2}\times x+\frac{2}{3}=\frac{5}{2}\)

\(\frac{1}{2}\times x=\frac{5}{2}-\frac{2}{3}\)

\(\frac{1}{2}\times x=\frac{11}{6}\)

\(x=\frac{11}{6}\div\frac{1}{2}\)

\(x=\frac{11}{3}\)

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

\(\frac{1}{2}x=\frac{5}{2}-\frac{2}{3}=\frac{11}{6}\)

\(x=\frac{11}{6}\div\frac{1}{2}\)

\(x=\frac{11}{3}\)

\(\frac{1}{2}.x-\frac{3}{4}=\frac{5}{6}\)

\(\frac{1}{2}.x=\frac{5}{6}+\frac{3}{4}\)

\(\frac{1}{2}.x=\frac{19}{12}\)

\(x=\frac{19}{12}:\frac{1}{2}\)

\(x=\frac{19}{6}\)

Vậy \(x=\frac{19}{6}\)

\(\frac{1}{2}\)x X = \(\frac{5}{6}\)+ \(\frac{3}{4}\)

\(\frac{1}{2}\)x X = \(\frac{19}{12}\)

X = \(\frac{19}{12}\): \(\frac{1}{2}\)

X = \(\frac{19}{6}\)

1/2 x X - 3/4 = 5/6

1/2 x X = 5/6 + 3/4

1/2 x X = 19/12

X = 19/12 : 1/2

X = 19/6