4. Решите уравнение: 5 a) x-1=2\frac{1}{7}; 6) (12\frac{5}{13}+y)-9\frac{9}{13}=7\frac{7}{13}.

a) $$x - 1 \frac{5}{7} = 2 \frac{1}{7}$$

$$x = 2 \frac{1}{7} + 1 \frac{5}{7}$$

$$x = 3 \frac{6}{7}$$

Ответ: $$3 \frac{6}{7}$$

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

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

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

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

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

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

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

Ответ: $$4 \frac{11}{13}$$