\(a.\dfrac{-4}{7}-\dfrac{5}{13}\times\dfrac{-39}{25}+\dfrac{-1}{42}:\dfrac{-5}{6}\) 

\(=\dfrac{-4}{7}+\dfrac{3}{5}+\dfrac{1}{35}\) \(=\dfrac{1}{35}+\dfrac{1}{35}=\dfrac{2}{35}\) 

\(b.\dfrac{2}{9}\times\left[\dfrac{4}{5}:\left(\dfrac{1}{5}-\dfrac{2}{15}\right)+1\dfrac{2}{3}\right]-\dfrac{-5}{27}\) 

\(=\dfrac{2}{9}\times\left[\dfrac{4}{5}:\dfrac{1}{15}+\dfrac{5}{3}\right]-\dfrac{-5}{27}\) 

\(=\dfrac{2}{9}\times\left(12+\dfrac{5}{3}\right)-\dfrac{-5}{27}\) 

\(=\dfrac{2}{9}\times\dfrac{41}{3}-\dfrac{-5}{27}=\dfrac{82}{27}-\dfrac{-5}{27}=\dfrac{29}{9}\)

133/99

quy đòng r tính nha ra \(\dfrac{199}{33}\)

a) y=10

b) y=7

\(a,\Rightarrow y=\dfrac{2\cdot5}{1}=10\\ b,\Rightarrow\dfrac{y}{5}=\dfrac{42}{25}:\dfrac{6}{5}=\dfrac{7}{5}\Rightarrow y=7\)

Ta có: \(2x^3-1=15\Leftrightarrow x^3=8\Rightarrow x=2\)

\(\Rightarrow\dfrac{18}{9}=\dfrac{y-25}{16}=\dfrac{z+9}{25}\Rightarrow\left\{{}\begin{matrix}\dfrac{y-25}{16}=2\Rightarrow y=57\\\dfrac{z+9}{25}=2\Rightarrow z=41\end{matrix}\right.\)

Vậy \(B=x+y+z=2+57+41=100\)

`2x^3-1=15=>2x^3=16=>x^3=8=>x=2`

Có:`[x+16]/9=[y-25]/16`

`=>[2+16]/9=[y-25]/16=>y=57`

Có:`[x+16]/9=[z+9]/25`

`=>[2+16]/9=[z+9]/25=>z=41`

Ta có:`B=x+y+z=2+57+41=100`

giúp mik nhoa mik đag cần gấp hihi

a) \(x=\dfrac{-3.\left(-5\right)}{15}=1\)

b) \(x=\dfrac{5.1173}{3}=1955\)

c) Tách làm 2 phép tính

(1) \(\dfrac{y}{15}=\dfrac{-25}{75}\rightarrow y=\dfrac{-25.15}{75}=-5\)

(2) \(\dfrac{2}{x}=\dfrac{-25}{75}\rightarrow x=\dfrac{75.2}{-25}=-6\)

\(\dfrac{20}{45};\dfrac{32}{72}\)

\(\dfrac{20}{45},\dfrac{32}{72},\)

12/27=20/45=32/72

2x^3-1=15

=>2x^3=16

=>x=2

(x+16)/9=(y-5)/16=(z+9)/25

=>(y-5)/16=(z+9)/25=2

=>y-5=32 và z+9=50

=>y=37 và z=41

B=x+y+z=2+37+41=80

a: \(\Leftrightarrow\dfrac{32}{x}=\dfrac{2}{15}+\dfrac{2}{35}+...+\dfrac{2}{99}\)

=>32/x=1/3-1/5+1/5-1/7+...+1/9-1/11

=>32/x=1/3-1/11=8/33

=>x=32:8/33=132

b: \(\Leftrightarrow1-\dfrac{1}{6}+1-\dfrac{1}{12}+...+1-\dfrac{1}{56}=\dfrac{x}{16}\)
\(\Leftrightarrow6-\left(\dfrac{1}{2}-\dfrac{1}{3}+\dfrac{1}{3}-\dfrac{1}{4}+...+\dfrac{1}{7}-\dfrac{1}{8}\right)=\dfrac{x}{16}\)

=>x/16=6-1/2+1/8=11/2+1/8=45/8=90/16

=>x=90

c: \(\Leftrightarrow\dfrac{22}{x}=\left(1-\dfrac{1}{2}\right)\left(1+\dfrac{1}{2}\right)\cdot\left(1-\dfrac{1}{3}\right)\left(1+\dfrac{1}{3}\right)\cdot...\cdot\left(1-\dfrac{1}{10}\right)\left(1+\dfrac{1}{10}\right)\)

=>22/x=1/2*2/3*...*9/10*3/2*4/3*...*11/10

=>22/x=1/10*11/2=11/20=22/40

=>x=40