Tìm x, biết:a) 0,75 - x =  - 0,6;b) 4/3:x =- 8/9;

a) \(0,75 - x =  - 0,6\)

\(x = 0,75 - \left( { - 0,6} \right)\)

\(x = 0,75 + 0,6\)

\(x = 1,35\)

Vậy \(x = 1,35\).

b) \(\frac{4}{3}:x = \frac{{ - 8}}{9}\)

\(x = \frac{4}{3}:\frac{{ - 8}}{9}\)

\(x = \frac{4}{3}.\frac{9}{{ - 8}}\)

\(x =  - \frac{3}{2}\)

Vậy \(x =  - \frac{3}{2}\).

c) \(27{\left( {3x - \frac{1}{5}} \right)^3} =  - 8\)

\({\left( {3x - \frac{1}{5}} \right)^3} =  - \frac{8}{{27}} = {\left( { - \frac{2}{3}} \right)^3}\)

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

\(3x =  - \frac{2}{3} + \frac{1}{5}\)

\(3x =  - \frac{7}{{15}}\)

\(x =  - \frac{7}{{45}}\)

Vậy \(x =  - \frac{7}{{45}}\).