1) y = -2.5x = 12
$$x = \frac{12}{-2.5} = -\frac{12}{2.5} = -\frac{120}{25} = -\frac{24}{5} = -4.8$$
2) y = 4x + 3 = $$\frac{2}{3}$$
$$4x = \frac{2}{3} - 3 = \frac{2}{3} - \frac{9}{3} = -\frac{7}{3}$$
$$x = \frac{-\frac{7}{3}}{4} = -\frac{7}{3 \cdot 4} = -\frac{7}{12}$$
Ответ:
1) x = -4.8
2) $$x = -\frac{7}{12}$$