а) Решим уравнение:
$$\frac{7}{12}y - 1 \frac{1}{4} = 0$$
$$\frac{7}{12}y - \frac{5}{4} = 0$$
$$\frac{7}{12}y = \frac{5}{4}$$
$$y = \frac{5}{4} : \frac{7}{12}$$
$$y = \frac{5}{4} \cdot \frac{12}{7}$$
$$y = \frac{5 \cdot 12}{4 \cdot 7} = \frac{5 \cdot 3}{1 \cdot 7} = \frac{15}{7} = 2 \frac{1}{7}$$
Ответ: $$y = 2 \frac{1}{7}$$