a) $$\frac{1}{4} + \frac{1}{7} = \frac{7}{28} + \frac{4}{28} = \frac{7+4}{28} = \frac{11}{28}$$
Ответ: $$\frac{11}{28}$$
б) $$\frac{1}{4} - \frac{1}{5} = \frac{5}{20} - \frac{4}{20} = \frac{5-4}{20} = \frac{1}{20}$$
Ответ: $$\frac{1}{20}$$
в) $$\frac{1}{2} - \frac{3}{8} = \frac{4}{8} - \frac{3}{8} = \frac{4-3}{8} = \frac{1}{8}$$
Ответ: $$\frac{1}{8}$$
г) $$\frac{1}{3} - \frac{1}{5} = \frac{5}{15} - \frac{3}{15} = \frac{5-3}{15} = \frac{2}{15}$$
Ответ: $$\frac{2}{15}$$
д) $$4 + \frac{4}{7} = \frac{4 \cdot 7}{7} + \frac{4}{7} = \frac{28}{7} + \frac{4}{7} = \frac{28+4}{7} = \frac{32}{7} = 4\frac{4}{7}$$
Ответ: $$4\frac{4}{7}$$
e) $$\frac{3}{4} + \frac{5}{6} = \frac{3 \cdot 3}{12} + \frac{5 \cdot 2}{12} = \frac{9}{12} + \frac{10}{12} = \frac{9+10}{12} = \frac{19}{12} = 1\frac{7}{12}$$
Ответ: $$1\frac{7}{12}$$