а)

\frac{7}{12} - \frac{5}{12}

;
б)

\frac{9}{10} + \frac{3}{10}

;
в)

\frac{1}{18} + \frac{11}{18}

;
г)

\frac{11}{15} - \frac{2}{15}

а) 7 12 − 5 12 ; б) 9 10 + 3 10 ; в) 1 18 + 11 18 ; г) 11 15 − 2 15 .

\frac{7}{12} - \frac{5}{12} = \frac{7 - 5}{12} = \frac{2}{12} = \frac{1}{6}

\frac{9}{10} + \frac{3}{10} = \frac{9 + 3}{10} = \frac{12}{10} = \frac{6}{5} = 1 \frac{1}{5}

\frac{1}{18} + \frac{11}{18} = \frac{1 + 11}{18} = \frac{12}{18} = \frac{2}{3}

\frac{11}{15} - \frac{2}{15} = \frac{11 - 2}{15} = \frac{9}{15} = \frac{3}{5}