Đáp án:
$\begin{array}{l}
a)x + \dfrac{1}{{12}} = - \dfrac{3}{8}\\
\Rightarrow x = - \dfrac{3}{8} - \dfrac{1}{{12}}\\
\Rightarrow x = \dfrac{{ - 9 - 2}}{{24}}\\
\Rightarrow x = - \dfrac{{11}}{{24}}\\
b)\text{thiếu}\,\text{đề}\\
c)\dfrac{2}{{15}} - x = \dfrac{{ - 3}}{{10}}\\
\Rightarrow x = \dfrac{2}{{15}} - \left( { - \dfrac{3}{{10}}} \right)\\
\Rightarrow x = \dfrac{2}{{15}} + \dfrac{3}{{10}}\\
\Rightarrow x = \dfrac{{4 + 9}}{{30}}\\
\Rightarrow x = \dfrac{{13}}{{30}}\\
d) - x + \dfrac{4}{5} = \dfrac{1}{2}\\
\Rightarrow x = \dfrac{4}{5} - \dfrac{1}{2}\\
\Rightarrow x = \dfrac{3}{{10}}\\
e)x.\left( { - \dfrac{3}{7}} \right) = \dfrac{5}{{21}}\\
\Rightarrow x = \dfrac{5}{{21}}.\dfrac{{ - 7}}{3}\\
\Rightarrow x = \dfrac{{ - 5}}{9}\\
f)\dfrac{{14}}{9}.x = \dfrac{{28}}{9}\\
\Rightarrow x = \dfrac{{28}}{9}.\dfrac{9}{{14}}\\
\Rightarrow x = 2\\
l)x:\left( { - \dfrac{2}{5}} \right) = \dfrac{{ - 15}}{{16}}\\
\Rightarrow x = \dfrac{{ - 15}}{{16}}.\left( { - \dfrac{2}{5}} \right)\\
\Rightarrow x = \dfrac{3}{8}\\
m) - \dfrac{4}{5}:x = - \dfrac{2}{5}\\
\Rightarrow x = - \dfrac{4}{5}:\left( { - \dfrac{2}{5}} \right)\\
\Rightarrow x = \dfrac{{ - 4}}{5}.\dfrac{5}{{ - 2}}\\
\Rightarrow x = 2\\
n)x + \dfrac{1}{3} = \dfrac{2}{5} - \left( { - \dfrac{1}{3}} \right)\\
\Rightarrow x = \dfrac{2}{5} + \dfrac{1}{3} - \dfrac{1}{3}\\
\Rightarrow x = \dfrac{2}{5}\\
i)\dfrac{3}{7} - x = \dfrac{1}{4} - \left( { - \dfrac{3}{5}} \right)\\
\Rightarrow x = \dfrac{3}{7} - \dfrac{1}{4} - \dfrac{3}{5}\\
\Rightarrow x = \dfrac{{60 - 35 - 3.28}}{{140}}\\
\Rightarrow x = \dfrac{{ - 49}}{{140}} = \dfrac{{ - 7}}{{20}}
\end{array}$
