Решение:
$$y = 2\frac{7}{12} - 4\frac{11}{15}$$
$$y = \frac{2*12 + 7}{12} - \frac{4*15 + 11}{15}$$
$$y = \frac{31}{12} - \frac{71}{15}$$
Общий знаменатель: 60
$$y = \frac{31 * 5}{12 * 5} - \frac{71 * 4}{15 * 4}$$
$$y = \frac{155}{60} - \frac{284}{60}$$
$$y = \frac{-129}{60}$$
$$y = -2\frac{9}{60}$$
$$y = -2\frac{3}{20}$$
Ответ: $$y = -2\frac{3}{20}$$