Tìm x, biết: 9/12 - x =  - 3/5

a) \(\frac{9}{{12}} - x = - \frac{3}{5}\)

\(x = \frac{9}{{12}} - \left( { - \frac{3}{5}} \right)\)

\(x = \frac{3}{4} + \frac{3}{5}\)

\(x = \frac{{27}}{{20}}\)

Vậy \(x = \frac{{27}}{{20}}.\)

b) \[x + 1,05 = 0,2 - 4,25\]

\[x + 1,05 = - 4,05\]

\[x = - 4,05 - 1,05\]

\[x = - 5,1\].

Vậy \[x = - 5,1.\]

c) \(\frac{1}{2}\left( {x - \frac{2}{3}} \right) - \frac{1}{3}\left( {2x - 3} \right) = x\)

\(\frac{1}{2}x - \frac{1}{3} - \frac{2}{3}x + 1 - x = 0\)

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

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

\(\frac{{ - 7}}{6}x + \frac{2}{3} = 0\)

\(\frac{{ - 7}}{6}x = - \frac{2}{3}\)

\(x = - \frac{2}{3}:\frac{{ - 7}}{6}\)

\(x = - \frac{2}{3} \cdot \frac{6}{{ - 7}}\)

\(x = \frac{4}{7}\)

Vậy \(x = \frac{4}{7}.\)