a. \(\dfrac{-3}{12}+\dfrac{1}{-4}=\dfrac{-3}{12}+\dfrac{-3}{12}=\dfrac{-3-3}{12}=\dfrac{-6}{12}=\dfrac{-1}{2}\)
 

b. \(\dfrac{5}{12}+\dfrac{-3}{28}=\dfrac{35}{84}+\dfrac{-9}{84}=\dfrac{35+\left(-9\right)}{84}=\dfrac{26}{84}=\dfrac{13}{42}\)
 

c. \(\dfrac{-7}{15}+\dfrac{3}{35}=\dfrac{-49}{105}+\dfrac{9}{105}=\dfrac{-49+9}{105}=\dfrac{-40}{105}=\dfrac{-8}{21}\)
 

d. \(\dfrac{-5}{7}+\dfrac{-3}{4}=\dfrac{-20}{28}+\dfrac{-21}{28}=\dfrac{-20+\left(-21\right)}{28}=\dfrac{-41}{28}\)

a ( ....< ....)

b( ....<....)

a <

b <

tick cho mk nha

a: \(=\dfrac{1}{3}\cdot\dfrac{1}{3}\cdot\dfrac{-17}{18}\cdot\dfrac{14}{17}=\dfrac{-14}{18\cdot9}=\dfrac{-14}{162}=\dfrac{-7}{81}\)

b: \(=\dfrac{12}{4}+\dfrac{35}{11}\cdot\dfrac{121}{245}=3+\dfrac{11}{7}=\dfrac{32}{7}\)

a: \(=\dfrac{15}{135}\cdot\dfrac{-17}{18}\cdot\dfrac{14}{17}=\dfrac{1}{9}\cdot\dfrac{-7}{9}=\dfrac{-7}{81}\)

b: \(=3+\dfrac{35}{11}\cdot\dfrac{121}{245}=3+\dfrac{11}{7}=\dfrac{32}{7}\)

\(\Rightarrow\dfrac{15}{x}=\dfrac{7}{28}-\dfrac{3}{4}\\ \Rightarrow\dfrac{15}{x}=\dfrac{-2}{4}\\ \Rightarrow15.4=x.\left(-2\right)=60\\ \Rightarrow x=60:\left(-2\right)=-30\\ \Rightarrow x=-30\)

5/14.1/3.-4/15:5/7=-2/45

nha bn

\(=\dfrac{5\cdot1\cdot\left(-4\right)\cdot7}{14\cdot3\cdot15\cdot5}=\dfrac{\left(-4\right)}{2\cdot3\cdot15}=\dfrac{-4}{90}=-\dfrac{2}{45}\)

\(\dfrac{5}{14}.\dfrac{1}{3}.\dfrac{-4}{15}:\dfrac{5}{7}=\dfrac{5}{14}.\dfrac{1}{3}.\dfrac{-4}{15}.\dfrac{7}{5}=\left(\dfrac{5}{14}.\dfrac{7}{5}\right).\left(\dfrac{1}{3}.\dfrac{-4}{15}\right)=\dfrac{1}{2}.\dfrac{-4}{45}=\dfrac{-2}{45}\)

a: \(x\cdot\dfrac{3}{4}+x=\dfrac{7}{8}\)

\(\Leftrightarrow x\cdot\dfrac{7}{4}=\dfrac{7}{8}\)

\(\Leftrightarrow x=\dfrac{1}{2}\)

`(x-3/8) +1/4= 7/8`

`=> x-3/8 = 7/8-1/4`

`=> x-3/8 = 7/8-2/8`

`=> x-3/8 =5/8`

`=>x= 5/8 +3/8`

`=>x= 8/8=1`