a)-12(x-5)+7(3-x)=5

-12x-(-60)+21-7x=5

-12x+60+21-7x=5

-12x-7x=5-60-21

-19x=-76

x=-76/-19

x=4. Vậy x=4

ặc, bạn ghi ít ít thôi, ghi thế này nhiều quá

\(\dfrac{15}{8}\)

x : 5/9 = 3/72

      x : 5/9 = 1/24

      x = 1/24 x 5/9

      x = 5 / 216

\(x:\dfrac{5}{9}=\dfrac{3}{72}\)

\(x=\dfrac{3}{72}\cdot\dfrac{5}{9}\)

\(x=\dfrac{5}{216}\)

72-3|x+1|=9

<=>3|x+1|=63

<=>|x+1|=21

Xét TH1: x+1>0

 <=>x+1=21

<=>x=20

Xét TH2: x+1<0

<=>x+1=-21

<=>x=-22

Vậy x=20 hoặc x=-22

a)  x = 1 4 + 4 7 ⇔ x = 1.7 + 4.4 28 = 23 28 ⇔ x = − 23 28 x = 23 28

b)  x − 1 = 7 2 + − 4 − 3 ⇔ x − 1 = 29 6 ⇔ x − 1 = 29 6 x − 1 = − 29 6 ⇔ x = 35 6 x = − 23 6

sorry em ko biết

a) \(\frac{5}{12}=\frac{x}{72}\Rightarrow x=\frac{5.72}{12}=30\)

b)\(\frac{x+3}{15}=\frac{1}{3}\)

\(\Rightarrow x+3=\frac{15.1}{3}=5\)

\(\Rightarrow x=5-3=2\)

c)\(\frac{-2}{9}=\frac{x}{72}\Rightarrow x=\frac{-2.72}{9}=-16\)

a) 5/12=30/72

b) 2+3/15=1/3

c) -2/9=-16/72

Chắc chắn đúng nha các bạn !

Ủng hộ mình nha các bạn !

x/3=y/5 => x+y/3+5=72/8=9

+,x/3=9=>x=27

+,y/5=9=>y=45

\(\frac{x}{3}=\frac{y}{5}\Rightarrow\frac{x}{3}:\frac{y}{5}=1\Rightarrow\frac{x}{3}.\frac{5}{y}=1\Rightarrow\frac{x}{y}=\frac{3}{5}\)

mà \(x+y=72\)

vậy +) \(x=\frac{3}{5+3}-72\)

             \(=\frac{3}{8}-72\)

             \(=27\)

        +) \(y=72-27\)

              \(=45\) 

thank trc  ^__^

Ta có:

1/30+1/42+1/56+1/72+1/90+1/110+1/132 -x = 2/3

=>1/(5.6) + 1/(6.7) + 1/(7.8) + (1/8.9) + 1/(9.10) + 1/(10.11) + 1/(11.12) - x = 2/3

=>1/5-1/6+1/6-1/7+...+1/11-1/12 - x = 2/3

=>1/5-1/12 - x = 2/3

=>7/60 - x = 2/3

=> x = 7/60 - 2/3

=> x = -11/20

Ta có:

1/30+1/42+1/56+1/72+1/90+1/110+1/132 -x = 2/3

=>1/(5.6) + 1/(6.7) + 1/(7.8) + (1/8.9) + 1/(9.10) + 1/(10.11) + 1/(11.12) - x = 2/3

=>1/5-1/6+1/6-1/7+...+1/11-1/12 - x = 2/3

=>1/5-1/12 - x = 2/3

=>7/60 - x = 2/3

=> x = 7/60 - 2/3

=> x = -11/20