a) Thực hiện phép tính (bằng cách hợp lí nếu có thể):

a) \[\frac{4}{7}.\frac{7}{3} + \frac{9}{5}.\frac{{ - 5}}{4}\]

 \[\frac{4}{7}.\frac{7}{3} + \frac{9}{5}.\frac{{ - 5}}{4}\]

\[ = \frac{4}{3} - \frac{9}{4}\]

 \( = \frac{{16}}{{12}} - \frac{{27}}{{12}}\)

 \( =  - \frac{9}{{12}} =  - \frac{3}{4}\)

b)

 \[\frac{2}{3} - \frac{1}{3}x = 1\]

 \[\frac{1}{3}x = \frac{2}{3} - 1\]

 \[\frac{1}{3}x = \frac{2}{3} - \frac{3}{3}\]

 \(\frac{1}{3}x =  - \frac{1}{3}\).

  \(x =  - \frac{1}{3}:\frac{1}{3} =  - 1\)

Vậy \(x =  - 1.\)