Tìm x, biết: a) − 3/5 + x = 1/2 ; b) 5/2 − 9/5 x = 2 1/4 ;

a) \(\frac{{ - 3}}{5} + x = \frac{1}{2}\)

     \(x = \frac{1}{2} + \frac{3}{5}\)

     \(x = \frac{{11}}{{10}}\)

Vậy \(x = \frac{{11}}{{10}}\).

b) \(\frac{5}{2} - \frac{9}{5}x = 2\frac{1}{4}\)

     \(\frac{9}{5}x = \frac{5}{2} - 2\frac{1}{4}\)

    \(\frac{9}{5}x = \frac{1}{4}\)

    \(x = \frac{1}{4}:\frac{9}{5}\)

    \(x = \frac{5}{{36}}\)

Vậy \(x = \frac{5}{{36}}\).

c) \(\left| {x - \frac{2}{3}} \right| - 2 =  - 0,5\)

    \(\left| {x - \frac{2}{3}} \right| =  - 0,5 + 2 = 1,5\)

Trường hợp 1:

\(x - \frac{2}{3} = 1,5\)

\(x = \frac{3}{2} + \frac{2}{3}\)

\(x = \frac{{13}}{6}\)

Vậy \(x \in \left\{ {\frac{{13}}{6};\frac{{ - 5}}{6}} \right\}\).

Trường hợp 2:

\(x - \frac{2}{3} =  - 1,5\)

\(x = \frac{{ - 3}}{2} + \frac{2}{3}\)

\(x = \frac{{ - 5}}{6}\)