Thực hiện phép tính (tính hợp lí nếu có thể) (a) − 18/5 + 4/5 . (b) − 1/4 − 3/4 .

a) \(\frac{{ - 18}}{5} + \frac{4}{5}\)\( = \frac{{ - 14}}{5}\)

b) \(\frac{{ - 1}}{4} - \frac{3}{4}\)\( = \frac{{ - 1}}{4} + \frac{{ - 3}}{4}\)\( = \frac{{ - 4}}{4} = - 1\)

c) \(\frac{{ - 5}}{{12}} + \frac{7}{3} + \frac{{ - 7}}{{12}}\)\( = \left( {\frac{{ - 5}}{{12}} + \frac{{ - 7}}{{12}}} \right) + \frac{7}{3}\)\( = \frac{{ - 12}}{{12}} + \frac{7}{3}\)\( = - 1 + \frac{7}{3}\)\( = \frac{{ - 3}}{3} + \frac{7}{3} = \frac{4}{3}\).