Ta có (7+x)/12=2/3

  suy ra 3(7+x)=24

  suy ra 7+x=8

          x=1

Ta có (25-x)/18=1/2

suy ra 2(25-x)=18

suy ra 25-x=9

         x=16

a,x=-76

b,x=441

mai mk học rồi , giúp nha, I x I là giá trị tuyệt đối của x !!!

Tìm x thuoc z:

1) \(26-\left|x+9\right|=-13\)

\(\Leftrightarrow\left|x+9\right|=26-\left(-13\right)\)

\(\Leftrightarrow\left|x+9\right|=39\)

\(\Leftrightarrow\left[{}\begin{matrix}x+9=39\\x+9=-39\end{matrix}\right.\)

\(\Leftrightarrow\left[{}\begin{matrix}x=39-9=30\\x=-39-9=-48\end{matrix}\right.\)

Vậy: \(x\in\left\{30;-48\right\}\)

2) \(\left|x+7\right|-13=25\)

\(\Leftrightarrow\left|x+7\right|=25+13=38\)

\(\Leftrightarrow x+7\in\left\{38;-38\right\}\)

\(\Leftrightarrow x\in\left\{31;-45\right\}\)

Vậy:.................

tim x biet

\(1)123-3.\left(x+4\right)=23\)

\(\Leftrightarrow3\left(x+4\right)=123-23\)

\(\Leftrightarrow3\left(x+4\right)=100\)

\(\Leftrightarrow x+4=\frac{100}{3}\)

\(\Leftrightarrow x=\frac{100}{3}-4=\frac{100-12}{3}=\frac{88}{3}\)

Vậy:................

2) Tương tự

a, 1-[15+11­] = x-[25-9]

1-16=x-16

-15=-x-16

x=-15+16

x=1

b,2-x=17-[-5]

2-x=17+5

2-x=22

x=2-22

x=-20

c, x-12=[-9­]-15

x-12=-24

x=-24+12

x=-12

d,9-25=[ 7- x­] -[25+7]

-16=[7-x]-32

[7-x]-32=-16

7-x=-16+32

7-x=16

x=7-16

x=-9

a)x-2/5=3/8

(x-2).8=5.3

x-2=5.3:8

x-2=1

=>x=3

b,c )tương tự

\(25\%x-\frac{7}{8}+x=\frac{2}{3}x\)

<=> \(\frac{1}{4}x-\frac{7}{8}+1x=\frac{2}{3}x\)

<=> \(\frac{1}{4}x+1x-\frac{2}{3}x=\frac{7}{8}\)

<=> \(x\left(\frac{1}{4}+1-\frac{2}{3}\right)=\frac{7}{8}\)

<=> \(x\cdot\frac{7}{12}=\frac{7}{8}\)

<=> \(x=\frac{12}{8}=\frac{3}{2}\)

Bài làm:

Ta có: \(25\%x-\frac{7}{8}+x=\frac{2}{3}x\)

\(\Leftrightarrow\frac{x}{4}+x-\frac{2}{3}x=\frac{7}{8}\)

\(\Leftrightarrow\frac{7}{12}x=\frac{7}{8}\)

\(\Leftrightarrow x=\frac{3}{2}\)