a) Ta có: \(\left(3.25-\dfrac{2}{3}x\right):\dfrac{-7}{4}=-3\)
\(\Leftrightarrow-\dfrac{2}{3}x+\dfrac{13}{4}=-3\cdot\dfrac{-7}{4}=\dfrac{21}{4}\)
\(\Leftrightarrow-\dfrac{2}{3}x=2\)
hay \(x=-2:\dfrac{2}{3}=-2\cdot\dfrac{3}{2}=-3\)
Vậy: x=-3
b) Ta có: \(\dfrac{7}{4}-\dfrac{3}{4}:x=\dfrac{7}{16}\)
\(\Leftrightarrow\dfrac{3}{4}:x=\dfrac{7}{4}-\dfrac{7}{16}=\dfrac{28}{16}-\dfrac{7}{16}=\dfrac{21}{16}\)
hay \(x=\dfrac{3}{4}:\dfrac{21}{16}=\dfrac{3}{4}\cdot\dfrac{16}{21}=\dfrac{4}{7}\)
Vậy: \(x=\dfrac{4}{7}\)
c) Ta có: \(\dfrac{5}{2}-\dfrac{3}{4}x=\dfrac{4}{5}\)
\(\Leftrightarrow\dfrac{3}{4}x=\dfrac{5}{2}-\dfrac{4}{5}=\dfrac{25}{10}-\dfrac{8}{10}=\dfrac{17}{10}\)
hay \(x=\dfrac{17}{10}:\dfrac{3}{4}=\dfrac{17}{10}\cdot\dfrac{4}{3}\)
hay \(x=\dfrac{34}{15}\)
Vậy: \(x=\dfrac{34}{15}\)
d) Ta có: \(\dfrac{3}{5}x+\dfrac{-1}{2}=\dfrac{-7}{10}\)
\(\Leftrightarrow\dfrac{3}{5}x=\dfrac{-7}{10}-\dfrac{-1}{2}=\dfrac{-7}{10}+\dfrac{1}{2}=\dfrac{-7}{10}+\dfrac{5}{10}=\dfrac{-2}{10}=\dfrac{-1}{5}\)
hay \(x=\dfrac{-1}{5}:\dfrac{3}{5}=\dfrac{-1}{5}\cdot\dfrac{5}{3}=\dfrac{-1}{3}\)
Vậy: \(x=-\dfrac{1}{3}\)
e) Ta có: \(\dfrac{4}{15}:x+\dfrac{-1}{3}=\dfrac{5}{9}\)
\(\Leftrightarrow\dfrac{4}{15}:x=\dfrac{5}{9}+\dfrac{1}{3}=\dfrac{8}{9}\)
\(\Leftrightarrow x=\dfrac{4}{15}:\dfrac{8}{9}=\dfrac{4}{15}\cdot\dfrac{9}{8}=\dfrac{36}{120}=\dfrac{3}{10}\)
Vậy: \(x=\dfrac{3}{10}\)
`a)(3,25-2/3x):((-7)/4)=-3`
`<=>3,25-2/3x=-3*(-7)/4=21/4`
`<=>13/4-2/3x=21/4`
`<=>2/3x=13/4-21/4=-8/4=-2`
`<=>x=-3`
`b)7/4-3/4:x=7/16`
`<=>3/4:x=7/4-7/16`
`<=>3/4:x=21/16`
`<=>x=3/4:21/16=4/7`
`c)5/2-3/4x=4/5`
`<=>3/4x=17/10`
`<=>x=34/15`
`d)3/5x+(-1)/2=-7/10`
`<=>3/5x=-7/10+1/2=-2/10=-1/5`
`<=>x=-1/3`
`e)4/15:x+(-1)/3=5/9`
`<=>4/15:x=5/9+1/3=8/9`
`<=>x=3/10`