82. Вычислите значение выражения: a) $14\frac{9}{13} - 1\frac{5}{13} + 12\frac{11}{13}$; б) $7\frac{24}{25} - 3\frac{12}{25} - 1\frac{7}{25}$; в) $17\frac{7}{40} + 3\frac{9}{40} - 1\frac{17}{40}$; г) $23\frac{15}{49} - 13\frac{19}{49} - 1\frac{30}{49}$

a) $14\frac{9}{13} - 1\frac{5}{13} + 12\frac{11}{13} = (14-1+12) + (\frac{9}{13} - \frac{5}{13} + \frac{11}{13}) = 25 + \frac{15}{13} = 25 + 1\frac{2}{13} = 26\frac{2}{13}$ б) $7\frac{24}{25} - 3\frac{12}{25} - 1\frac{7}{25} = (7-3-1) + (\frac{24}{25} - \frac{12}{25} - \frac{7}{25}) = 3 + \frac{5}{25} = 3\frac{1}{5}$ в) $17\frac{7}{40} + 3\frac{9}{40} - 1\frac{17}{40} = (17+3-1) + (\frac{7}{40} + \frac{9}{40} - \frac{17}{40}) = 19 + \frac{-1}{40} = 18\frac{39}{40}$ г) $23\frac{15}{49} - 13\frac{19}{49} - 1\frac{30}{49} = 22\frac{64}{49} - 13\frac{19}{49} - 1\frac{30}{49} = (22 - 13 - 1) + (\frac{64}{49} - \frac{19}{49} - \frac{30}{49}) = 8 + \frac{15}{49} = 8\frac{15}{49}$