\begin{multicols}{2}
\text{}

\vspace{-\baselineskip}
$\begin{aligned}
A&= \frac{ \frac{1}{2}-\frac{1}{3}+\frac{2}{5}+\frac{1}{6}}{
\frac{1}{2}+\frac{1}{3}-\frac{2}{5}-\frac{5}{6}}  \\
A&= \frac{\frac{15}{30}-\frac{10}{30}+\frac{12}{30}+\frac{5}{30}}{
\frac{15}{30}+\frac{10}{30}-\frac{12}{30}-\frac{25}{30}} \\
A&= \dfrac{\frac{22}{30}}{\frac{-12}{30}} \\
A&= -\frac{22}{12} \\
A&= -\frac{11}{6}.
\end{aligned}$
\columnbreak
\text{}

% \vspace*{-1mm}
\hspace{2mm} $\begin{aligned}
 B&= \frac{(5^2\times 10^{-5})^3}{(5\times
10^{-3})^5}\times\left(\frac{10^2}{5}\right)^2 \\
B &= \frac{5^6\times 10^{-15}}{5^5\times
10^{-15}}\times \frac{10^4}{5^2} \\
B &= 5\times \frac{(5\times 2)^4}{5^2} \\
B  &= \frac{5\times 5^4 \times 2^4 }{5^2} \\
B  &= 5^3 \times 2^4.
\end{aligned}$
\vfill
\text{}
\end{multicols}

$\displaystyle C=2^{23}\times \left (\frac{1}{2}\right
)^{24}=\frac{2^{23}}{2^{24}}=\frac{1}{2}.$

$\displaystyle D=\left (\frac{2}{3}\right )^{108}\times \left
(\frac{3}{2}\right)^{107}
=\left (\frac{2}{3}\right )^{108}\div\left (\frac{2}{3}\right )^{107}
=\frac{2}{3}.$

$\displaystyle a=0,000\,073\,654=\numprint{7,3654}\times10^{-5}.$

$\displaystyle b=9\,325\,000=9,325\times10^6.$

$\displaystyle c=0,023\times 10^{-5}=2,3\times10^{-2}\times 10^{-5}=2,3.10^{-7}.$

$\displaystyle d=19,402\times 10^2=\numprint{1,9402}\times10^3.$

