172. Выполните действия: 1) \(\frac{5}{9} + \frac{1}{9}\); 2) \(\frac{8}{17} - \frac{2}{17}\); 3) \(\frac{8}{25} - \frac{3}{25} + \frac{9}{25}\); 4) \(\frac{21}{57} + \frac{31}{57} - \frac{9}{57}\).

\(\frac{5}{9} + \frac{1}{9} = \frac{5+1}{9} = \frac{6}{9} = \frac{2}{3}\)

\(\frac{8}{17} - \frac{2}{17} = \frac{8-2}{17} = \frac{6}{17}\)

\(\frac{8}{25} - \frac{3}{25} + \frac{9}{25} = \frac{8-3+9}{25} = \frac{5+9}{25} = \frac{14}{25}\)

\(\frac{21}{57} + \frac{31}{57} - \frac{9}{57} = \frac{21+31-9}{57} = \frac{52-9}{57} = \frac{43}{57}\)