Đáp án:
i. \(x = \dfrac{5}{2}\)
Giải thích các bước giải:
\(\begin{array}{l}
a.\dfrac{x}{6} = \dfrac{8}{3}\\
\to 3x = 24\\
\to x = 8\\
b.\dfrac{x}{6} = \dfrac{7}{4}\\
\to 4x = 42\\
\to x = \dfrac{{21}}{2}\\
c.\dfrac{x}{3} = \dfrac{5}{{24}}\\
\to 24x = 15\\
\to x = \dfrac{{15}}{{24}}\\
\to x = \dfrac{5}{8}\\
d.\dfrac{{1,2}}{{30}} = \dfrac{{3x + 4}}{5}\\
\to \dfrac{1}{{25}} = \dfrac{{3x + 4}}{5}\\
\to 5 = 75x + 100\\
\to 75x = - 95\\
\to x = - \dfrac{{19}}{{15}}\\
e.DK:x \ne - \dfrac{5}{3}\\
\dfrac{3}{7} = \dfrac{{2x + 1}}{{3x + 5}}\\
\to 9x + 15 = 14x + 7\\
\to 5x = 8\\
\to x = \dfrac{8}{5}\\
f.\dfrac{{2x + 3}}{{3x + 1}} = \dfrac{3}{4}\\
\to 8x + 12 = 9x + 3\\
\to x = 9\\
g.\dfrac{{6x - 5}}{{ - 7}} = \dfrac{{5x - 3}}{{ - 5}}\\
\to \dfrac{{6x - 5}}{7} = \dfrac{{5x - 3}}{5}\\
\to 30x - 25 = 35x - 21\\
\to 5x = - 4\\
\to x = - \dfrac{4}{5}\\
h.\dfrac{{12 - 7x}}{{ - 13}} = \dfrac{{4 - 3x}}{{ - 5}}\\
\to \dfrac{{12 - 7x}}{{13}} = \dfrac{{4 - 3x}}{5}\\
\to 60 - 35x = 52 - 39x\\
\to 4x = - 8\\
\to x = - 2\\
i.DK:x \ne - 1\\
\dfrac{{2x - 3}}{{x + 1}} = \dfrac{4}{7}\\
\to 14x - 21 = 4x + 4\\
\to 10x = 25\\
\to x = \dfrac{5}{2}
\end{array}\)
