Đáp án:
$\begin{array}{l}
1)a)2,5 - \left( { - \frac{2}{7}} \right) = \frac{4}{{10}} + \frac{2}{7} = \frac{{28}}{{70}} + \frac{{20}}{{70}} = \frac{{48}}{{70}} = \frac{{24}}{{35}}\\
b)\left( {\frac{{ - 1}}{8} + \frac{{ - 5}}{{16}}} \right).\left| {\frac{{ - 4}}{7}} \right|\\
= \left( {\frac{{ - 2}}{{16}} - \frac{5}{{16}}} \right).\frac{4}{7}\\
= \frac{{ - 7}}{{16}}.\frac{4}{7}\\
= \frac{{ - 1}}{4}\\
2)\,{16^5} - {2^{15}}\\
= {\left( {{2^4}} \right)^5} - {2^{15}}\\
= {2^{20}} - {2^{15}}\\
= {2^{15}}\left( {{2^5} - 1} \right)\\
= {2^{15}}.\left( {32 - 1} \right)\\
= {2^{15}}.31 \vdots 31\\
3)x:y = 2:\left( { - 3} \right)\\
\Rightarrow \frac{x}{2} = \frac{y}{{ - 3}} = \frac{{x + y}}{{2 - 3}} = \frac{{ - 2016}}{{ - 1}} = 2016\\
\Rightarrow \left\{ \begin{array}{l}
x = 2016.2 = 2032\\
y = 2016.\left( { - 3} \right) = - 6048
\end{array} \right.
\end{array}$
