518. Выполните действие: a) $\frac{1}{3} + \frac{1}{5}$; б) $\frac{1}{3} - \frac{1}{4}$; в) $2\frac{1}{9} + 1\frac{1}{3}$; г) $2\frac{1}{2} - 1\frac{1}{3}$; д) $3 - 1\frac{1}{5}$; e) $\frac{2}{3} \cdot \frac{3}{4}$; ж) $4 \cdot \frac{5}{6}$; з) $\frac{5}{9} : 1\frac{1}{5}$; и) $1\frac{1}{3} \cdot \frac{3}{4}$; к) $2\frac{1}{4} : 1\frac{1}{3}$

a) $\frac{1}{3} + \frac{1}{5} = \frac{5}{15} + \frac{3}{15} = \frac{8}{15}$ б) $\frac{1}{3} - \frac{1}{4} = \frac{4}{12} - \frac{3}{12} = \frac{1}{12}$ в) $2\frac{1}{9} + 1\frac{1}{3} = 2\frac{1}{9} + 1\frac{3}{9} = 3\frac{4}{9}$ г) $2\frac{1}{2} - 1\frac{1}{3} = \frac{5}{2} - \frac{4}{3} = \frac{15}{6} - \frac{8}{6} = \frac{7}{6} = 1\frac{1}{6}$ д) $3 - 1\frac{1}{5} = 3 - \frac{6}{5} = \frac{15}{5} - \frac{6}{5} = \frac{9}{5} = 1\frac{4}{5}$ e) $\frac{2}{3} \cdot \frac{3}{4} = \frac{2 \cdot 3}{3 \cdot 4} = \frac{6}{12} = \frac{1}{2}$ ж) $4 \cdot \frac{5}{6} = \frac{4 \cdot 5}{6} = \frac{20}{6} = \frac{10}{3} = 3\frac{1}{3}$ з) $\frac{5}{9} : 1\frac{1}{5} = \frac{5}{9} : \frac{6}{5} = \frac{5}{9} \cdot \frac{5}{6} = \frac{25}{54}$ и) $1\frac{1}{3} \cdot \frac{3}{4} = \frac{4}{3} \cdot \frac{3}{4} = \frac{4 \cdot 3}{3 \cdot 4} = \frac{12}{12} = 1$ к) $2\frac{1}{4} : 1\frac{1}{3} = \frac{9}{4} : \frac{4}{3} = \frac{9}{4} \cdot \frac{3}{4} = \frac{27}{16} = 1\frac{11}{16}$