a, 2 × $\frac{5}{18}$ = $\frac{5}{9}$
b, $\frac{3}{8}$ ÷ $\frac{7}{5}$ = $\frac{15}{56}$ ;
$\frac{3}{4}$ ÷ $\frac{9}{10}$ = $\frac{5}{6}$ ;
$\frac{7}{8}$ ÷ 2 = $\frac{7}{16}$ ;
6 ÷ $\frac{2}{3}$ = 9
c, $\frac{1}{3}$ × $\frac{3}{5}$ × $\frac{5}{9}$ = $\frac{1}{9}$
$\frac{15}{16}$ ÷ $\frac{3}{8}$ × $\frac{3}{4}$ = $\frac{15}{8}$