2 Вычислите: a) $$\frac{1}{3}$$ + 2$$\frac{2}{5}$$; б) 5$$\frac{7}{8}$$ - 3$$\frac{11}{12}$$; в) 6$$\frac{3}{7}$$\cdot$$2$$\frac{1}{9}$$; г) 12$$\frac{2}{3}$$: 2$$\frac{5}{7}$$.

a) $$\frac{1}{3}$$ + 2$$\frac{2}{5}$$ = $$\frac{1}{3}$$ + $$\frac{2 \cdot 5 + 2}{5}$$ = $$\frac{1}{3}$$ + $$\frac{12}{5}$$ = $$\frac{1 \cdot 5 + 12 \cdot 3}{15}$$ = $$\frac{5 + 36}{15}$$ = $$\frac{41}{15}$$ = 2$$\frac{11}{15}$$

Ответ: 2$$\frac{11}{15}$$

б) 5$$\frac{7}{8}$$ - 3$$\frac{11}{12}$$ = $$\frac{5 \cdot 8 + 7}{8}$$ - $$\frac{3 \cdot 12 + 11}{12}$$ = $$\frac{47}{8}$$ - $$\frac{47}{12}$$ = $$\frac{47 \cdot 3 - 47 \cdot 2}{24}$$ = $$\frac{141 - 94}{24}$$ = $$\frac{47}{24}$$ = 1$$\frac{23}{24}$$

Ответ: 1$$\frac{23}{24}$$

в) 6$$\frac{3}{7}$$\cdot$$2$$\frac{1}{9}$$ = $$\frac{6 \cdot 7 + 3}{7}$$\cdot$$\frac{2 \cdot 9 + 1}{9}$$ = $$\frac{45}{7}$$\cdot$$\frac{19}{9}$$ = $$\frac{5}{7}$$\cdot$$\frac{19}{1}$$ = $$\frac{95}{7}$$ = 13$$\frac{4}{7}$$

Ответ: 13$$\frac{4}{7}$$

г) 12$$\frac{2}{3}$$: 2$$\frac{5}{7}$$ = $$\frac{12 \cdot 3 + 2}{3}$$: $$\frac{2 \cdot 7 + 5}{7}$$ = $$\frac{38}{3}$$: $$\frac{19}{7}$$ = $$\frac{38}{3}$$\cdot$$\frac{7}{19}$$ = $$\frac{2}{3}$$\cdot$$\frac{7}{1}$$ = $$\frac{14}{3}$$ = 4$$\frac{2}{3}$$

Ответ: 4$$\frac{2}{3}$$