Tìm x, biết: a) 1/2:x = 0,6;    b) x - 5/6=  - 2/3

a) \(\frac{1}{2}:x = 0,6\)

\(x = 0,5:0,6\)

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

Vậy \(x = \frac{5}{6}\).

b) \(x - \frac{5}{6} =  - \frac{2}{3}\)

\(x =  - \frac{2}{3} + \frac{5}{6}\)

\(x =  - \frac{4}{6} + \frac{5}{6}\)

\(x = \frac{1}{6}\)

Vậy \(x = \frac{1}{6}\).

c) \[\left( {\frac{2}{3} - 2x} \right)\left( {x + \frac{4}{5}} \right) = 0\]

Suy ra \[\frac{2}{3} - 2x = 0\] hoặc \[x + \frac{4}{5} = 0\]

Trường hợp 1:

\[\frac{2}{3} - 2x = 0\]

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

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

Vậy \[x \in \left\{ {\frac{1}{3};\frac{{ - 4}}{5}} \right\}\].

Trường hợp 2:

\[x + \frac{4}{5} = 0\]

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