a) (14 \frac{9}{13} - 1 \frac{5}{13} + 12 \frac{11}{13} = 13 \frac{4}{13} + 12 \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} = 4 \frac{12}{25} - 1 \frac{7}{25} = 3 \frac{5}{25})