Đáp án:
$\begin{array}{l}
a)x:8 = 5:4\\
\Leftrightarrow x = \dfrac{5}{4}.8\\
\Leftrightarrow x = 10\\
Vậy\,x = 10\\
b)2,5:7,5 = x:\dfrac{3}{5}\\
\Leftrightarrow \dfrac{1}{3} = x:\dfrac{3}{5}\\
\Leftrightarrow x = \dfrac{1}{3}.\dfrac{3}{5}\\
\Leftrightarrow x = \dfrac{1}{5}\\
Vậy\,x = \dfrac{1}{5}\\
c)2\dfrac{2}{3}:x = 1\dfrac{7}{9}:0,2\\
\Leftrightarrow \dfrac{8}{3}:x = \dfrac{{16}}{9}:\dfrac{1}{5}\\
\Leftrightarrow \dfrac{8}{3}:x = \dfrac{{16}}{9}.5 = \dfrac{{80}}{9}\\
\Leftrightarrow x = \dfrac{8}{3}:\dfrac{{80}}{9}\\
\Leftrightarrow x = \dfrac{8}{3}.\dfrac{9}{{80}}\\
\Leftrightarrow x = \dfrac{3}{{10}}\\
Vậy\,x = \dfrac{3}{{10}}\\
d)\left( {x - 1} \right):1,5 = 2,8:0,5\\
\Leftrightarrow \left( {x - 1} \right):\dfrac{3}{2} = \dfrac{{28}}{5}\\
\Leftrightarrow x - 1 = \dfrac{{28}}{5}.\dfrac{3}{2}\\
\Leftrightarrow x - 1 = \dfrac{{42}}{5}\\
\Leftrightarrow x = \dfrac{{42}}{5} + 1\\
\Leftrightarrow x = \dfrac{{47}}{5}\\
Vậy\,x = \dfrac{{47}}{5}\\
e)0,6:x = x:2,4\\
\Leftrightarrow \dfrac{{0,6}}{x} = \dfrac{x}{{2,4}}\\
\Leftrightarrow x.x = 0,6.2,4\\
\Leftrightarrow {x^2} = 1,44\\
\Leftrightarrow x = 1,2;x = - 1,2\\
Vậy\,x = 1,2;x = - 1,2
\end{array}$
