$\frac{4,6}{х + 4,4} = \frac{8,4}{3х + 5,1}$
4,6 * (3х + 5,1) = (х + 4,4) * 8,4
13,8х + 23,46 = 8,4х + 36,96
13,8х − 8,4х = 36,96 − 23,46
5,4х = 13,5
х = 2,5

$\frac{2\frac{2}{3}}{х + \frac{1}{3}} = \frac{1\frac{1}{2}}{х - 1\frac{1}{8}}$
$2\frac{2}{3} * (х - 1\frac{1}{8}) = 1\frac{1}{2} * (х + \frac{1}{3})$
$\frac{8}{3} * (х - \frac{9}{8}) = \frac{3}{2} * (х + \frac{1}{3})$
$\frac{8}{3}х - 3 = \frac{3}{2}х + \frac{1}{2}$
$\frac{8}{3}х - \frac{3}{2}х = \frac{1}{2} + 3$
$\frac{16}{6}х - \frac{9}{6}х = 3\frac{1}{2}$
$\frac{7}{6}х = \frac{7}{2}$
$х = \frac{7}{2} : \frac{7}{6}$
$х = \frac{7}{2} * \frac{6}{7}$
х = 3