Вычисли наиболее удобным способом:

а) $\frac{12}{13} + \frac{4}{16} + \frac{1}{13} + \frac{3}{16} = (\frac{12}{13} + \frac{1}{13}) + (\frac{4}{16} + \frac{3}{16}) = \frac{13}{13} + \frac{7}{16} = 1 + \frac{7}{16} = 1\frac{7}{16}$ б) $(\frac{13}{50} + \frac{8}{27}) + (\frac{6}{27} + \frac{37}{50}) = (\frac{13}{50} + \frac{37}{50}) + (\frac{8}{27} + \frac{6}{27}) = \frac{50}{50} + \frac{14}{27} = 1 + \frac{14}{27} = 1\frac{14}{27}$ в) $(\frac{28}{33} + \frac{2}{3}) - \frac{28}{33} = (\frac{28}{33} - \frac{28}{33}) + \frac{2}{3} = 0 + \frac{2}{3} = \frac{2}{3}$ г) $(\frac{6}{7} + \frac{18}{19}) - \frac{18}{19} = \frac{6}{7} + (\frac{18}{19} - \frac{18}{19}) = \frac{6}{7} + 0 = \frac{6}{7}$ д) $\frac{25}{57} - (\frac{2}{57} + \frac{23}{57}) = \frac{25}{57} - \frac{25}{57} = 0$ е) $2 - (1\frac{1}{3} + \frac{2}{3}) = 2 - (1 + \frac{1}{3} + \frac{2}{3}) = 2 - (1 + 1) = 2 - 2 = 0$