Đáp án:
$\begin{array}{l}
a)19\dfrac{5}{8}:1\dfrac{5}{7} - 15\dfrac{5}{8}:\dfrac{{12}}{7} - 1\dfrac{1}{3}\\
= 19\dfrac{5}{8}:\dfrac{{12}}{7} - 15\dfrac{5}{8}:\dfrac{{12}}{7} - \dfrac{4}{3}\\
= \left( {19\dfrac{5}{8} - 15\dfrac{5}{8}} \right):\dfrac{{12}}{7} - \dfrac{4}{3}\\
= \left( {4\dfrac{5}{8}} \right):\dfrac{{12}}{7} - \dfrac{4}{3}\\
= \dfrac{{37}}{8}.\dfrac{7}{{12}} - \dfrac{4}{3}\\
= \dfrac{{259}}{{96}} - \dfrac{4}{3} = \dfrac{{131}}{{96}}\\
b)\dfrac{2}{5}.\dfrac{1}{3} - \dfrac{2}{{15}}:\dfrac{1}{5} + \dfrac{3}{5}.\dfrac{1}{3}\\
= \dfrac{2}{{15}} - \dfrac{2}{{15}}.5 + \dfrac{3}{{15}}\\
= \dfrac{{2 - 10 + 3}}{{15}} = \dfrac{{ - 5}}{{15}} = - \dfrac{1}{3}\\
c){\left( {\dfrac{2}{5}} \right)^2} + 5\dfrac{1}{2}\left( {4,5 - 2} \right) + \dfrac{{{2^3}}}{{\left( { - 4} \right)}}\\
= \dfrac{4}{{25}} + \dfrac{{11}}{2}.2,5 - 2\\
= \dfrac{4}{{25}} + \dfrac{{11}}{2}.\dfrac{5}{2} - 2\\
= \dfrac{4}{{25}} + \dfrac{{55}}{4} - 2\\
= \dfrac{{16 + 55.25 - 2.100}}{{100}}\\
= \dfrac{{1191}}{{100}}\\
d)2,5.\dfrac{7}{{19}} + \dfrac{5}{2}.\dfrac{3}{{19}} - 2\dfrac{1}{2}.\dfrac{{15}}{{19}}\\
= \dfrac{5}{2}.\dfrac{7}{{19}} + \dfrac{5}{2}.\dfrac{3}{{19}} - \dfrac{5}{2}.\dfrac{{15}}{{19}}\\
= \dfrac{5}{2}.\left( {\dfrac{7}{{19}} + \dfrac{3}{{19}} - \dfrac{{15}}{{19}}} \right)\\
= \dfrac{5}{2}.\dfrac{{ - 5}}{{19}}\\
= \dfrac{{ - 25}}{{38}}
\end{array}$
