Tìm số hữu tỉ x biết:

a)

 \[x + \frac{2}{3} = 2\frac{1}{{18}}\]

\[x + \frac{2}{3} = \frac{{37}}{{18}}\]

 \(x = \frac{{37}}{{18}} - \frac{2}{3}\)

 \(x = \frac{{25}}{{18}}\)

b)

 \[\frac{3}{4} - \frac{1}{5}x = 1,25\]

\[\frac{3}{4} - \frac{1}{5}x = \frac{5}{4}\]

 \[\frac{1}{5}x = \frac{3}{4} - \frac{5}{4}\]

 \[\frac{1}{5}x = - \frac{1}{2}\]

  \(x = \frac{{ - 1}}{2}:\frac{1}{5}\)

  \(x = - \frac{5}{2}\)