$\frac{x - 8}{x + 2} = \frac{7}{3}$
3(x − 8) = 7(x + 2)
3x − 24 = 7x + 14
3x − 7x = 14 + 24
−4x = 38
$x = -\frac{38}{4}$
$x = -\frac{19}{2} = -9\frac{1}{2}$

$\frac{4}{x - 1,2} = \frac{15}{x - 10}$
4(x − 10) = 15(x − 1,2)
4x − 40 = 15x − 18
4x − 15x = −18 + 40
−11x = 22
x = 22 : (−11)
x = −2