a) $$\frac{3}{7} * 6 = \frac{3*6}{7} = \frac{18}{7}$$
б) $$\frac{5}{8} : 2 = \frac{5}{8*2} = \frac{5}{16}$$
в) $$\frac{7}{17} * 5 = \frac{7*5}{17} = \frac{35}{17}$$
г) $$\frac{7}{9} : 3 = \frac{7}{9*3} = \frac{7}{27}$$
д) $$\frac{3}{8} * 16 = \frac{3*16}{8} = \frac{48}{8} = 6$$
е) $$\frac{4}{5} : 12 = \frac{4}{5*12} = \frac{4}{60} = \frac{1}{15}$$