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

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

=> -19x+81=5

=>-19x=5-81

=>-19x=-76

=>x=4

Vậy x=4

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

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

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

-19x + 81 = 5

-19x = 5 - 81

-19x = -76

x = -76 : (-19)

x = 4

Ta có \(-12.\left(x-5\right)+7.\left(3-x\right)=5\)

\(\Rightarrow-12x+60+21-21x=5\)

\(\Rightarrow\left(-12x-21x\right)+\left(60+21\right)=5\)

\(\Rightarrow-33x+81=5\)

\(\Rightarrow-33x=-77\)

\(\Rightarrow x=\frac{7}{3}\)

\(\frac{4}{5}\)+ \(\frac{1}{5}\): \(\frac{-2}{15}\)= \(\frac{4}{5}\)+ \(\frac{1}{5}\)* \(\frac{-15}{2}\)=\(\frac{4}{5}\) + \(\frac{-3}{2}\)= \(\frac{-7}{10}\)

b = \(\frac{-7}{12}\). (\(\frac{3}{11}\)+ \(\frac{-14}{11}\)) + \(\frac{5}{6}\)= \(\frac{-7}{12}\). (-1) + \(\frac{5}{6}\)= \(\frac{7}{12}\)+ \(\frac{10}{12}\)= \(\frac{17}{12}\)

x-\(\frac{3}{5}\)x = \(\frac{2}{5}\)

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

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

=> x=1

Vậy x=1

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

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

=> -19x = -76

=> x= 4 

b) 30. (x+2) -6. (x-5 ) -24x =100

=> 30x + 60 - 6x + 30 -24x = 100

=>  0x = 10 (vô lí )

=> ko có giá trị của x

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

(-12).x-(-12).5+7.3-7.x=5

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

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

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

(-12).x+81-7.x=5

(-12).x-7.x=5-81

-19.x=-76

x=76:(-19)

x=4

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

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

<=> -19x + 81 = 5 

<=> -19x = -76

=> x = 4

b, 30(x + 2) - 6(x - 5) - 24x = 100

<=> 30x + 60 - 6x + 30 - 24x = 100

<=> 0x + 90 = 100

<=> 0x = 10

=> x = O

a) \(\dfrac{13}{20}+\dfrac{3}{5}+x=\dfrac{5}{6}\)

\(\Rightarrow\dfrac{5}{4}+x=\dfrac{5}{6}\)

\(\Rightarrow x=\dfrac{5}{6}-\dfrac{5}{4}\)

\(\Rightarrow x=\dfrac{-5}{12}\)

b) \(x+\dfrac{1}{3}=\dfrac{2}{5}-\dfrac{-1}{3}\)

\(\Rightarrow x+\dfrac{1}{3}=\dfrac{11}{15}\)

\(\Rightarrow x=\dfrac{11}{15}-\dfrac{1}{3}\)

\(\Rightarrow x=\dfrac{2}{5}\)

c)\(\dfrac{-5}{8}-x=\dfrac{-3}{20}-\dfrac{-1}{6}\)

\(\dfrac{-5}{8}-x=\dfrac{1}{60}\)

\(\Rightarrow x=\dfrac{-5}{8}-\dfrac{1}{60}\)

\(\Rightarrow x=\dfrac{-77}{120}\)

d) \(\dfrac{3}{5}-x=\dfrac{1}{4}+\dfrac{7}{10}\)

\(\Rightarrow\dfrac{3}{5}-x=\dfrac{19}{20}\)

\(\Rightarrow x=\dfrac{3}{5}-\dfrac{19}{20}\)

\(\Rightarrow x=\dfrac{-7}{20}\)

e) \(\dfrac{-3}{7}-x=\dfrac{4}{5}+\dfrac{-2}{3}\)

\(\Rightarrow\dfrac{-3}{7}-x=\dfrac{2}{15}\)

\(\Rightarrow x=\dfrac{-3}{7}-\dfrac{2}{15}\)

\(\Rightarrow x=\dfrac{-59}{105}\)

g) \(\dfrac{-5}{6}-x=\dfrac{7}{12}+\dfrac{-1}{3}\)

\(\Rightarrow\dfrac{-5}{6}-x=\dfrac{1}{4}\)

\(\Rightarrow x=\dfrac{-5}{6}-\dfrac{1}{4}\)

\(\Rightarrow x=\dfrac{-13}{12}\)