Thực hiện các phép tính sau: (a) 7/9 − 8/3 + 5/6 . (b) − 3/4 . 20/21 + 7/10 : 49/50 .

a) \(\frac{7}{9} - \frac{8}{3} + \frac{5}{6}\)

\[ = \frac{{14}}{{18}} - \frac{{48}}{{18}} + \frac{{15}}{{18}}\]

\[ = \frac{{ - 19}}{{18}}.\]

b) \(\frac{{ - 3}}{4}.\frac{{20}}{{21}} + \frac{7}{{10}}:\frac{{49}}{{50}}\)

\( = \frac{{ - 5}}{7} + \frac{5}{7} = 0.\)