Thực hiện phép tính (tính hợp lí nếu có thể): a) \[\frac{7}{{30}} + \frac{{ - 12}}{{37}} + \frac{{23}}{{30}} + \frac{{ - 25}}{{37}}.\]         b) \(\left( { - 0,4} \right) \cdot \left( { -

a) \[\frac{7}{{30}} + \frac{{ - 12}}{{37}} + \frac{{23}}{{30}} + \frac{{ - 25}}{{37}}\]

\[ = \left( {\frac{7}{{30}} + \frac{{23}}{{30}}} \right) + \left( {\frac{{ - 12}}{{37}} + \frac{{ - 25}}{{37}}} \right)\]

\[ = 1 + \left( { - 1} \right) = 0.\]

c) \(\frac{2}{{11}}.\frac{{ - 5}}{4} + \frac{{ - 9}}{{11}}.\frac{5}{4} + 1\frac{3}{4}\)

\( = \frac{2}{{11}} \cdot \frac{{ - 5}}{4} + \frac{9}{{11}} \cdot \frac{{ - 5}}{4} + \frac{7}{4}\)

\( = \frac{{ - 5}}{4} \cdot \left( {\frac{2}{{11}} + \frac{9}{{11}}} \right) + \frac{7}{4}\)

\( = \frac{{ - 5}}{4} \cdot \frac{{11}}{{11}} + \frac{7}{4}\)

\( = \frac{{ - 5}}{4} \cdot 1 + \frac{7}{4}\)

\[ = \frac{{ - 5}}{4} + \frac{7}{4}\]

\[ = \frac{2}{4} = \frac{1}{2}.\]

b) \(\left( { - 0,4} \right) \cdot \left( { - 0,5} \right) \cdot \left( { - 0,8} \right)\)

\[ = 0,2 \cdot \left( { - 0,8} \right)\]

\[ = - 0,16.\]

d) \(\left( {\frac{5}{7} \cdot 0,6 - 5:3\frac{1}{2}} \right) \cdot \left( {40\% - 1,4} \right) \cdot {\left( { - \frac{2}{3}} \right)^3}\)

\( = \left( {\frac{5}{7} \cdot \frac{3}{5} - 5:\frac{7}{2}} \right) \cdot \left( {\frac{2}{5} - \frac{7}{5}} \right) \cdot \left( { - \frac{8}{{27}}} \right)\)

\( = \left( {\frac{3}{7} - \frac{{10}}{7}} \right) \cdot \left( { - 1} \right) \cdot \left( { - \frac{8}{{27}}} \right)\)

\( = \left( { - 1} \right) \cdot \left( { - 1} \right) \cdot \left( { - \frac{8}{{27}}} \right)\)

\( = 1 \cdot \left( { - \frac{8}{{27}}} \right)\)

\( = - \frac{8}{{27}}.\)