3. Выполните сложение или вычитание.

Решение задания 3 (сложение и вычитание дробей с одинаковыми знаменателями): 1) $\frac{7}{12} + \frac{3}{12} = \frac{7+3}{12} = \frac{10}{12} = \frac{5}{6}$ 2) $\frac{3}{7} + \frac{2}{7} = \frac{5}{7}$ 3) $\frac{13}{55} - \frac{5}{55} = \frac{8}{55}$ 4) $\frac{11}{18} - \frac{7}{18} = \frac{4}{18} = \frac{2}{9}$ 5) $\frac{7}{10} + \frac{1}{10} = \frac{8}{10} = \frac{4}{5}$ 6) $\frac{15}{8} - \frac{7}{8} = \frac{8}{8} = 1$ 7) $\frac{12}{15} + \frac{7}{15} = \frac{19}{15} = 1\frac{4}{15}$ 8) $\frac{45}{100} + \frac{35}{100} = \frac{80}{100} = \frac{4}{5}$ 9) $\frac{65}{76} - \frac{25}{76} = \frac{40}{76} = \frac{10}{19}$ 10) $\frac{4}{5} - \frac{3}{5} = \frac{1}{5}$ 11) $\frac{4}{11} + \frac{6}{11} = \frac{10}{11}$ 12) $\frac{7}{8} - \frac{5}{8} = \frac{2}{8} = \frac{1}{4}$ 13) $\frac{76}{100} - \frac{67}{100} = \frac{9}{100}$ 14) $\frac{6}{13} + \frac{7}{13} = \frac{13}{13} = 1$ 15) $\frac{43}{56} - \frac{33}{56} = \frac{10}{56} = \frac{5}{28}$ 16) $\frac{6}{23} + \frac{20}{23} = \frac{26}{23} = 1\frac{3}{23}$ 17) $\frac{4}{7} + \frac{2}{7} = \frac{6}{7}$ 18) $\frac{3}{4} + \frac{3}{4} = \frac{6}{4} = 1\frac{2}{4} = 1\frac{1}{2}$ 19) $7 + \frac{1}{5} = 7\frac{1}{5}$ 20) $1 + 3\frac{5}{7} = 4\frac{5}{7}$ 21) $8\frac{2}{5} + 3 = 11\frac{2}{5}$ 22) $8\frac{7}{6} - 6 = 8\frac{7}{6} - 6 = 2\frac{7}{6} = 3\frac{1}{6}$ 23) $4 + 1\frac{3}{5} = 5\frac{3}{5}$