б) 1/3 x + 1/4 x - 1/12 x = 5;

б) $$ \frac{1}{3}x + \frac{1}{4}x - \frac{1}{12}x = 5$$
$$(\frac{1}{3}+\frac{1}{4}-\frac{1}{12})x=5$$
$$(\frac{4}{12}+ \frac{3}{12} - \frac{1}{12})x = 5$$
$$ \frac{6}{12}x = 5$$
$$\frac{1}{2}x = 5$$
$$x = 5 : \frac{1}{2}$$
$$x = 5 \cdot 2$$
$$x = 10$$

Ответ: 10