Đáp án:
\(A = \dfrac{{13}}{{168}}\)
Giải thích các bước giải:
\(\begin{array}{l}
A = \dfrac{1}{4} + \dfrac{2}{7} - \dfrac{1}{2} + \dfrac{3}{8} - \dfrac{3}{5} + \dfrac{4}{{15}}\\
= \left( {\dfrac{{2 - 4 + 3}}{8}} \right) + \dfrac{2}{7} + \left( {\dfrac{{ - 9 + 4}}{{15}}} \right)\\
= \dfrac{1}{8} + \dfrac{2}{7} - \dfrac{1}{3} = \dfrac{1}{8} + \dfrac{{6 - 7}}{{21}}\\
= \dfrac{1}{8} - \dfrac{1}{{21}} = \dfrac{{13}}{{168}}
\end{array}\)
