138. Выполните деление: а) $$\frac{14}{39}:\frac{21}{52}$$; б) $$4\frac{1}{11}:2\frac{19}{22}$$; в) $$18:\frac{9}{14}$$.

a) $$\frac{14}{39}:\frac{21}{52} = \frac{14}{39} \cdot \frac{52}{21} = \frac{14 \cdot 52}{39 \cdot 21} = \frac{2 \cdot 7 \cdot 4 \cdot 13}{3 \cdot 13 \cdot 3 \cdot 7} = \frac{8}{9}$$

б) $$4\frac{1}{11}:2\frac{19}{22} = \frac{45}{11}:\frac{63}{22} = \frac{45}{11} \cdot \frac{22}{63} = \frac{45 \cdot 22}{11 \cdot 63} = \frac{5 \cdot 9 \cdot 2 \cdot 11}{11 \cdot 7 \cdot 9} = \frac{10}{7} = 1\frac{3}{7}$$

в) $$18:\frac{9}{14} = 18 \cdot \frac{14}{9} = 2 \cdot 14 = 28$$

Ответ: а) $$\frac{8}{9}$$; б) $$1\frac{3}{7}$$; в) 28