Thực hiện phép tính (tính hợp lý nếu có thể) (a) 5/11 + 6/11 : − 3/2 .

a) \[\frac{5}{{11}}{\mkern 1mu} + {\mkern 1mu} \frac{6}{{11}}{\mkern 1mu} :{\mkern 1mu} \frac{{ - 3}}{2}{\mkern 1mu} = {\mkern 1mu} \frac{5}{{11}}{\mkern 1mu} + {\mkern 1mu} \frac{6}{{11}}{\mkern 1mu} \cdot{\mkern 1mu} \frac{{ - 2}}{3}{\mkern 1mu} = {\mkern 1mu} \frac{5}{{11}}{\mkern 1mu} + {\mkern 1mu} \frac{{ - 4}}{{11}}{\mkern 1mu} = {\mkern 1mu} \frac{{11}}{{11}}\]

b)\[\frac{7}{{36}} + \frac{4}{{21}} - 1\frac{{19}}{{36}} + \frac{{ - 25}}{{21}} + \frac{5}{6} = \left( {\frac{7}{{36}} - \frac{{55}}{{36}}} \right) + \left( {\frac{4}{{21}} - \frac{{25}}{{21}}} \right) + \frac{5}{6}\]\[ = {\mkern 1mu} \frac{{ - 48}}{{36}} + {\mkern 1mu} \frac{{ - 21}}{{21}}{\mkern 1mu} + {\mkern 1mu} \frac{5}{6} = {\mkern 1mu} \frac{{ - 4}}{3}{\mkern 1mu} - {\mkern 1mu} 1 + \frac{5}{6} = \frac{{ - 8}}{6} - \frac{6}{6} + \frac{5}{6} = \frac{{ - 9}}{6} = \frac{{ - 3}}{2}\]

c) \[ - 0,6\cdot\frac{8}{{19}} - \frac{3}{5}:\frac{{19}}{7} + 2\frac{9}{{19}} = - \frac{3}{5}\cdot\frac{8}{{19}} - \frac{3}{5}\cdot\frac{7}{{19}} + \frac{{47}}{{19}} = - \frac{3}{5}\cdot\left( {\frac{8}{{19}} + \frac{7}{{19}}} \right) + \frac{{47}}{{19}} = - \frac{3}{5}\cdot\frac{{15}}{{19}} + \frac{{47}}{{19}}\]

\[ = \frac{{ - 9}}{{19}} + \frac{{47}}{{19}} = \frac{{38}}{{19}} = 2\]