$\text{a) $\dfrac{3}{4}$ + $\dfrac{1}{4}$ : x = $\dfrac{2}{5}$}$ $\\$ $\text{$\dfrac{1}{4}$ : x = $\dfrac{2}{5}$}$ - $\dfrac{3}{4}$ $\\$ $\text{ $\dfrac{1}{4}$ : x = $\dfrac{-7}{20}$}$ $\\$ $\text{ x = $\dfrac{1}{4}$ : $\dfrac{-7}{20}$}$ $\\$ $\text{ x = $\dfrac{-5}{7}$}$ $\\$ $\text{Vậy: x = $\dfrac{-5}{7}$}$
$\text{b) $\dfrac{2}{3}$.x : $\dfrac{3}{5}$ = $\dfrac{1}{4}$}$ $\\$ $\text{$\dfrac{2}{3}$.x = $\dfrac{1}{4}$ . $\dfrac{3}{5}$}$ $\\$ $\text{$\dfrac{2}{3}$.x = $\dfrac{3}{20}$ }$ $\\$ $\text{x = $\dfrac{3}{20}$ : $\dfrac{2}{3}$ }$ $\\$ $\text{x = $\dfrac{9}{40}$ }$ $\\$ $\text{Vậy: x = $\dfrac{9}{40}$}$
$\text{c) $\dfrac{4}{3}$ : $\dfrac{2}{5}$.x = $\dfrac{1}{6}$}$ $\\$ $\text{ $\dfrac{10}{3}$.x = $\dfrac{1}{6}$}$ $\\$ $\text{ x = $\dfrac{1}{6}$ : $\dfrac{10}{3}$}$ $\\$ $\text{ x = $\dfrac{1}{20}$}$ $\\$ $\text{Vậy: x = $\dfrac{1}{20}$}$
@tryphena
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