5.175 Решите уравнение: a) x - 7/13 = 2/13 ; б) 13/17 - y = 3/17 ; в) z + 7/21 = 13/21 ; г) 9/29 + u = 18/29 .

a) $$x - \frac{7}{13} = \frac{2}{13}$$

$$x = \frac{2}{13} + \frac{7}{13}$$

$$x = \frac{2+7}{13}$$

$$x = \frac{9}{13}$$.

б) $$\frac{13}{17} - y = \frac{3}{17}$$

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

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

$$y = \frac{10}{17}$$.

в) $$z + \frac{7}{21} = \frac{13}{21}$$

$$z = \frac{13}{21} - \frac{7}{21}$$

$$z = \frac{13-7}{21}$$

$$z = \frac{6}{21} = \frac{2}{7}$$.

г) $$\frac{9}{29} + u = \frac{18}{29}$$

$$u = \frac{18}{29} - \frac{9}{29}$$

$$u = \frac{18-9}{29}$$

$$u = \frac{9}{29}$$.

Ответ: a) x = 9/13; б) y = 10/17; в) z = 2/7; г) u = 9/29.