Đáp án:
$\begin{array}{l}
1)a)1,2:0,8 = \left( { - 3,6} \right):3x\\
\Rightarrow 1,2:0,8 = - 1,2:x\\
\Rightarrow 0,8 = - x\\
\Rightarrow x = - 0,8\\
Vay\,x = - 0,8\\
b)x:2,5 = 0,03:0,75\\
\Rightarrow x:2,5 = \dfrac{3}{{75}} = \dfrac{1}{{25}}\\
\Rightarrow x = \dfrac{1}{{25}}.2,5\\
\Rightarrow x = \dfrac{1}{{25}}.\dfrac{{25}}{{10}}\\
\Rightarrow x = \dfrac{1}{{10}}\\
c)12:5 = x:1,5\\
\Rightarrow x = \dfrac{{12}}{5}.1,5\\
\Rightarrow x = 3,6\\
Vay\,x = 3,6\\
B2)\\
a)\dfrac{{2 - x}}{4} = \dfrac{{3x - 1}}{{ - 3}}\\
\Rightarrow - 3.\left( {2 - x} \right) = 4.\left( {3x - 1} \right)\\
\Rightarrow - 6 + 3x = 12x - 4\\
\Rightarrow 12x - 3x = - 6 + 4\\
\Rightarrow 9x = - 2\\
\Rightarrow x = - \dfrac{2}{9}\\
Vay\,x = - \dfrac{2}{9}\\
b)\dfrac{x}{{15}} = \dfrac{{60}}{x}\\
\Rightarrow x.x = 15.60\\
\Rightarrow {x^2} = 900\\
\Rightarrow \left[ \begin{array}{l}
x = 30\\
x = - 30
\end{array} \right.\\
c)\dfrac{{5 - 2x}}{3} = 4x - 1\\
\Rightarrow 5 - 2x = 3.\left( {4x - 1} \right)\\
\Rightarrow 5 - 2x = 12x - 3\\
\Rightarrow 12x + 2x = 5 + 3\\
\Rightarrow 14x = 8\\
\Rightarrow x = \dfrac{8}{{14}} = \dfrac{4}{7}\\
d)\dfrac{x}{{24}} = \dfrac{6}{x}\\
\Rightarrow x.x = 6.24\\
\Rightarrow {x^2} = 144\\
\Rightarrow \left[ \begin{array}{l}
x = 12\\
x = - 12
\end{array} \right.
\end{array}$
