Thực hiện phép tính (tính hợp lí nếu có thể): a) 7/30 + - 12/37 + 23/30 + - 25/37

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

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

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

b) \(\left( { - 1,6} \right) \cdot \left( { - 0,125} \right) \cdot \left( { - 0,5} \right)\)

\( = 0,2 \cdot \left( { - 0,5} \right)\)

\( = - 0,1.\)

c) \(\frac{2}{3}:\frac{4}{5} - \frac{5}{4} + \frac{1}{3}:\frac{4}{5}\)

\( = \frac{2}{3} \cdot \frac{5}{4} - \frac{5}{4} + \frac{1}{3} \cdot \frac{5}{4}\)

\( = \frac{5}{4} \cdot \left( {\frac{2}{3} - 1 + \frac{1}{3}} \right) = \frac{5}{4} \cdot \left[ {\left( {\frac{2}{3} + \frac{1}{3}} \right) - 1} \right]\)

\( = \frac{5}{4} \cdot \left[ {\frac{3}{3} - 1} \right] = \frac{5}{4} \cdot \left( {1 - 1} \right)\)

\( = \frac{5}{4} \cdot 0 = 0.\)

d) \[{\left( { - 2} \right)^3} \cdot \frac{{ - 1}}{{24}} + \left( {80\% - 1,2} \right):\frac{2}{{15}}\]

\( = \left( { - 8} \right) \cdot \frac{{ - 1}}{{24}} + \left( {\frac{4}{5} - \frac{6}{5}} \right) \cdot \frac{{15}}{2}\)

\( = \frac{1}{3} + \frac{{ - 2}}{5} \cdot \frac{{15}}{2}\)

\( = \frac{1}{3} + \left( { - 3} \right)\)

\( = \frac{1}{3} + \frac{{ - 9}}{3} = \frac{{ - 8}}{3}.\)