2. Реши уравнение у - \frac{4}{7}y = 4,2.

$$y - \frac{4}{7}y = 4,2$$

$$y(1-\frac{4}{7}) = 4,2$$

$$y(\frac{7}{7}-\frac{4}{7}) = 4,2$$

$$\frac{3}{7}y = 4,2$$

$$y = 4,2 : \frac{3}{7}$$

$$y = \frac{42}{10} \cdot \frac{7}{3}$$

$$y = \frac{14}{10} \cdot 7$$

$$y = \frac{98}{10} = 9,8$$

Ответ: $$y = 9,8$$