2. Выполните действия: a) 1/4 + 2/9; б) 3/7 - 1/10; в) 31/55 - 7/80; г) 3/8 + 3/14 - 1/28

a) \(\frac{1}{4} + \frac{2}{9} = \frac{9}{36} + \frac{8}{36} = \frac{17}{36}\) б) \(\frac{3}{7} - \frac{1}{10} = \frac{30}{70} - \frac{7}{70} = \frac{23}{70}\) в) \(\frac{31}{55} - \frac{7}{80} = \frac{31 \cdot 16}{55 \cdot 16} - \frac{7 \cdot 11}{80 \cdot 11} = \frac{496}{880} - \frac{77}{880} = \frac{419}{880}\) г) \(\frac{3}{8} + \frac{3}{14} - \frac{1}{28} = \frac{3 \cdot 7}{8 \cdot 7} + \frac{3 \cdot 4}{14 \cdot 4} - \frac{1 \cdot 2}{28 \cdot 2} = \frac{21}{56} + \frac{12}{56} - \frac{2}{56} = \frac{31}{56}\)