[tex]3)[/tex]

[tex]( \frac{3}{4} x - \frac{2}{5} ) + ( \frac{2}{3} x + 0.6) -( \frac{7}{12} x - 0.3) = 5.8 \\ \frac{3}{4} x - \frac{2}{5} + \frac{2}{3} x + \frac{6}{10} - \frac{7}{12} x - \frac{3}{10} = \frac{58}{10} \\ \frac{9x + 8x - 7x}{12} + \frac{ - 4 + 6 - 3}{10} = \frac{58}{10} \\ \frac{10}{12} x - \frac{1}{10} = \frac{58}{10} \\ \frac{10}{12} x = \frac{58}{10} + \frac{1}{10} = \frac{59}{10} \\ x = \frac{59}{10} \div \frac{10}{12} = \frac{59}{10} \times \frac{12}{10} \\ x = \frac{354}{50} = 7.08[/tex]