Thực hiện phép tính một cách hợp lí:

d) \(\frac{{\frac{1}{{29}} \cdot \frac{3}{2} - \frac{{26}}{{11}} \cdot \frac{3}{{23}} + \frac{9}{{238}}}}{{\frac{{ - 3}}{{29}} + \frac{{13}}{{11}} \cdot \frac{3}{{23}} - \frac{9}{{119}}}}.\)

a) \[\frac{{\frac{3}{4} + \frac{3}{5} + \frac{3}{7} - \frac{3}{{11}}}}{{\frac{6}{4} + \frac{6}{5} + \frac{6}{7} - \frac{6}{{11}}}} = \frac{{3 \cdot \left( {\frac{1}{4} + \frac{1}{4} + \frac{1}{7} - \frac{1}{{11}}} \right)}}{{6 \cdot \left( {\frac{1}{4} + \frac{1}{4} + \frac{1}{7} - \frac{1}{{11}}} \right)}} = \frac{3}{6} = \frac{1}{2}.\]

h) \[\frac{1}{3} + \frac{1}{{15}} + \frac{1}{{35}} + \frac{1}{{63}} + \frac{1}{{99}} + \frac{1}{{143}} + \frac{1}{{195}}\]

\( = \frac{1}{{1 \cdot 3}} + \frac{1}{{3 \cdot 5}} + \frac{1}{{5 \cdot 7}} + \frac{1}{{7 \cdot 9}} + \frac{1}{{9 \cdot 11}} + \frac{1}{{11 \cdot 13}} + \frac{1}{{13 \cdot 15}}\)

\( = \frac{1}{2} \cdot \left( {\frac{2}{{1 \cdot 3}} + \frac{2}{{3 \cdot 5}} + \frac{2}{{5 \cdot 7}} + \frac{2}{{7 \cdot 9}} + \frac{2}{{9 \cdot 11}} + \frac{2}{{11 \cdot 13}} + \frac{2}{{13 \cdot 15}}} \right)\)

\[ = \frac{1}{2} \cdot \left( {\frac{1}{1} - \frac{1}{3} + \frac{1}{3} - \frac{1}{5} + \frac{1}{5} - \frac{1}{7} + \frac{1}{7} - \frac{1}{9} + \frac{1}{9} - \frac{1}{{11}} + \frac{1}{{11}} - \frac{1}{{13}} + \frac{1}{{13}} - \frac{1}{{15}}} \right)\]

\[ = \frac{1}{2} \cdot \left( {\frac{1}{1} - \frac{1}{{15}}} \right) = \frac{1}{2} \cdot \left( {\frac{{15}}{{15}} - \frac{1}{{15}}} \right)\]

\[ = \frac{1}{2} \cdot \frac{{14}}{{15}} = \frac{7}{{15}}.\]