401. Решите уравнение: a) \frac{3}{5} + x = \frac{4}{5}; б) y - \frac{2}{7} = \frac{6}{7}; в) \frac{11}{25} - k = \frac{7}{25}; г) d + \frac{2}{9} = \frac{1}{9} + \frac{7}{9}.

a) \frac{3}{5} + x = \frac{4}{5} x = \frac{4}{5} - \frac{3}{5} x = \frac{1}{5} б) y - \frac{2}{7} = \frac{6}{7} y = \frac{6}{7} + \frac{2}{7} y = \frac{8}{7} в) \frac{11}{25} - k = \frac{7}{25} k = \frac{11}{25} - \frac{7}{25} k = \frac{4}{25} г) d + \frac{2}{9} = \frac{1}{9} + \frac{7}{9} d + \frac{2}{9} = \frac{8}{9} d = \frac{8}{9} - \frac{2}{9} d = \frac{6}{9} = \frac{2}{3}