4. Решите уравнение. x-1 5/7 =2 1/7 (x=3 6/7) (12 5/13 + y) - 9 9/13 =7 7/13 (y = 7 7/13

Решим уравнение:

$$(12 \frac{5}{13} + y) - 9 \frac{9}{13} = 7 \frac{7}{13}$$

$$12 \frac{5}{13} + y = 7 \frac{7}{13} + 9 \frac{9}{13}$$

$$12 \frac{5}{13} + y = 16 \frac{7+9}{13}$$

$$12 \frac{5}{13} + y = 16 \frac{16}{13}$$

$$12 \frac{5}{13} + y = 17 \frac{3}{13}$$

$$y = 17 \frac{3}{13} - 12 \frac{5}{13}$$

$$y = 16 \frac{16}{13} - 12 \frac{5}{13}$$

$$y = 4 \frac{16-5}{13}$$

$$y = 4 \frac{11}{13}$$

Ответ: $$y = 4 \frac{11}{13}$$