г) +3 = 4x - 3; 19 д) 25х+30 = х - 5. 6+5x

г) $$\frac{x+3}{19} = 4x - 3$$

$$x + 3 = 19(4x - 3)$$ $$x + 3 = 76x - 57$$ $$75x = 60$$ $$x = \frac{60}{75} = \frac{4}{5} = 0.8$$

Ответ: 0.8

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д) $$\frac{25x+30}{6+5x} = x - 5$$

$$25x + 30 = (x - 5)(6 + 5x)$$ $$25x + 30 = 6x + 5x^2 - 30 - 25x$$ $$5x^2 - 44x - 60 = 0$$

Найдем дискриминант:

$$D = (-44)^2 - 4 \cdot 5 \cdot (-60) = 1936 + 1200 = 3136 = 56^2$$

Тогда

$$x_{1,2} = \frac{44 \pm 56}{10}$$

$$x_1 = \frac{44 + 56}{10} = \frac{100}{10} = 10$$

$$x_2 = \frac{44 - 56}{10} = \frac{-12}{10} = -1.2$$

Ответ: $$x = 10; -1.2$$