a: \(=\dfrac{17}{19}\cdot\dfrac{19}{17}\cdot\dfrac{4}{5}=\dfrac{4}{5}\)

b: \(=\dfrac{14}{7}\cdot\dfrac{7}{6}=2\cdot\dfrac{7}{6}=\dfrac{14}{6}=\dfrac{7}{3}\)

c: =13/14(4/5+1/5)=13/14

\(\dfrac{17}{19}\times\dfrac{12}{15}\times\dfrac{19}{17}=\dfrac{12}{15}\)

\(\left(\dfrac{5}{7}+\dfrac{9}{7}\right)\times\dfrac{21}{18}=2\times\dfrac{7}{6}=\dfrac{7}{3}\)

\(\dfrac{4}{5}\times\dfrac{13}{14}+\dfrac{13}{14}\times\dfrac{1}{5}=\dfrac{13}{14}\)

\(\dfrac{17}{19}\times\dfrac{12}{15}\times\dfrac{19}{17}.\\ =\dfrac{17}{19}\times\dfrac{19}{17}\times\dfrac{12}{15}.\\ =1\times\dfrac{12}{15}=\dfrac{12}{15}.\\ \left(\dfrac{5}{7}+\dfrac{9}{7}\right)\times\dfrac{21}{18}.\\ =2\times\dfrac{7}{6}=\dfrac{7}{3}.\\ \dfrac{4}{5}\times\dfrac{13}{14}+\dfrac{13}{14}\times\dfrac{1}{5}.\\ =\left(\dfrac{4}{5}+\dfrac{1}{5}\right)\times\dfrac{13}{14}.\\ =1\times\dfrac{13}{14}.\\ =\dfrac{13}{14}.\)

\(\frac{9}{14}-\frac{x}{7}:\frac{5}{3}=\frac{3}{14}\Leftrightarrow\frac{9}{14}-\frac{3x}{35}=\frac{3}{14}\Leftrightarrow\frac{3x}{35}=\frac{3}{7}\Leftrightarrow3x=15\Leftrightarrow x=5\)

9/14-x/7:5/3=6/14

x/7:5/3=3/14

x/7=5/14

x=35/7

X = 35 thôi

\(x-14=3x+18\)

\(\Leftrightarrow\)\(3x-x=-14-18\)

\(\Leftrightarrow\)\(2x=-32\)

\(\Leftrightarrow\)\(x=\frac{-32}{2}\)

\(\Leftrightarrow\)\(x=-16\)

b) Ta có :

\(\left|x+3\right|\ge0\)\(;\)\(\left|x+9\right|\ge0\) và \(\left|x+5\right|\ge0\) nên \(\left|x+3\right|+\left|x+9\right|+\left|x+5\right|\ge0\)

Mà \(\left|x+3\right|+\left|x+9\right|+\left|x+5\right|=4x\) \(\Rightarrow\)\(4x\ge0\)

Vì \(4>0\) nên \(x\ge0\)

\(\Rightarrow\)\(\left|x+3\right|+\left|x+9\right|+\left|x+5\right|=4x\)

\(\Leftrightarrow\)\(x+3+x+9+x+5=4x\)

\(\Leftrightarrow\)\(\left(x+x+x\right)+\left(3+9+5\right)=4x\)

\(\Leftrightarrow\)\(3x+17=4x\)

\(\Leftrightarrow\)\(4x-3x=17\)

\(\Leftrightarrow\)\(x=17\)

Vậy \(x=17\)

\(x-14=3x+18\)

\(x-3x=14+18\)

\(-2x=32\)

\(x=\frac{32}{-2}\)

\(x=-16\)

\(x-14=3x+18\)

\(x-3x=14+18\)

\(-2x=32\)

\(x=32:\left(-2\right)\)

\(x=-16\)

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a.1/4

b.-7/144

c.25/21

d.17/7

e.80/63

f.9/7

a)1/4

b)-7/144

c)-25/21

d)17/7

e)16/63

f)9/7

\(5\frac{4}{9}+x-7\frac{7}{18}=15\frac{3}{4}\)

\(\frac{49}{9}+x-\frac{133}{18}=\frac{63}{4}\)

\(\frac{49}{9}+x=\frac{833}{36}\)

\(x=\frac{637}{36}\)