\(a,\dfrac{11}{12}-\left(\dfrac{2}{5}+x\right)=\dfrac{2}{3}\)

\(\dfrac{2}{5}+x=\dfrac{11}{12}-\dfrac{2}{3}\)

\(\dfrac{2}{5}+x=\dfrac{1}{4}\)

\(x=\dfrac{1}{4}-\dfrac{2}{5}\)

\(x=\dfrac{-3}{20}\)

Vậy ...

b, \(2x\left(x-\dfrac{1}{7}\right)=0\)

\(\Leftrightarrow\left[{}\begin{matrix}2x=0\\x-\dfrac{1}{7}=0\end{matrix}\right.\)

\(\Leftrightarrow\left[{}\begin{matrix}x=0\\x=\dfrac{1}{7}\end{matrix}\right.\)

Vậy ...

c, \(\dfrac{3}{4}+\dfrac{1}{4}:x=\dfrac{2}{5}\)

\(\dfrac{1}{4}:x=\dfrac{2}{5}-\dfrac{3}{4}\)

\(\dfrac{1}{4}:x=\dfrac{-7}{20}\)

\(x=\dfrac{1}{4}:\dfrac{-7}{20}\)

\(x=\dfrac{-5}{7}\)

Vậy ...

a)\(\dfrac{11}{12}-\left(\dfrac{2}{5}+x\right)=\dfrac{2}{3}\)

<=>\(\dfrac{2}{5}+x=\dfrac{1}{4}\)

<=>\(x=\dfrac{1}{4}-\dfrac{2}{5}\)

<=>\(x=-\dfrac{3}{20}\)

b)\(2x\left(x-\dfrac{1}{7}\right)=0\)

=>\(\text{2x=0 hoặc }x-\dfrac{1}{7}=0\)

=>\(x=0hoặcx=\dfrac{1}{7}\)

Vậy....

c)\(\dfrac{3}{4}+\dfrac{1}{4}:x=\dfrac{2}{5}\)

=>\(\dfrac{1}{4}:x=-\dfrac{7}{20}\)

=>x=\(-\dfrac{5}{7}\)

Vậy

25%.x+1/2.x=12

=> 1/4.x+1/2.x=12

=> x.(1/4+1/2)=12

=> x.0,75       =12

=> x              =12:0,75

=> x              =16

Vậy x=16

25/100.x + 1/2.x = 12

1/10.x + 1/2.x =12 

(1/10 + 1/2 ).x =12

( 1/10 + 5/10 ).x =12

6/10 = 3/5.x = 12

               x = 12 : 3/5

                x = 12 . 5/3

                x = 20

ax1phan2=a/2

\(a\times\frac{1}{2}=\frac{a}{2}\)

Vì số nào nhân với 1 cũng bằng chính số đó thôi

=\(\frac{a}{2}\)

`(1/3+2/5)xx3/9`

`=(5/15+6/15)xx1/3`

`=11/15xx1/3`

`=11/45`

ai đây???

có phải của real madrid ko nhỉ???

\(\frac{25-x}{18}=\frac{1}{2}\)

\(\frac{25-x}{18}=\frac{9}{18}\)

\(25-x=9\)

\(x=25-9\)

\(x=16\)