Tìm x, biết: a) 2/5 x + 3/5 = -3/5

a) \(\frac{3}{5} + \frac{2}{5}.x = \frac{{ - 3}}{4}\)

   \(\frac{2}{5}.x = \frac{{ - 3}}{4} - \frac{3}{5}\)

   \(\frac{2}{5}x = \frac{{ - 27}}{{20}}\)

   \(x = \frac{{ - 27}}{{20}}:\frac{2}{5}\)

    \(x = \frac{{ - 27}}{8}\)

Vậy \(x = \frac{{ - 27}}{8}.\)

b) \[\frac{7}{4} - \left( {x + \frac{3}{4}} \right) = - 0,4\]

    \(\frac{7}{4} - x - \frac{3}{4} = - 0,4\)

    \(1 - x = - 0,4\)

\(x = 1 - \left( { - 0,4} \right)\)

     \(x = 1,4\)

Vậy \(x = 1,4\).