一、口算。
$\frac{8}{9} ÷ \frac{4}{15} =$
$9 ÷ \frac{3}{4} =$
$\frac{3}{8} × 14 =$
$\frac{3}{7} × \frac{1}{3} =$
$\frac{9}{10} ÷ \frac{3}{20} =$
$14 ÷ \frac{7}{8} =$
$\frac{1}{5} × \frac{16}{25} =$
$\frac{11}{40} - \frac{1}{8} =$
$\frac{8}{3} ÷ \frac{12}{11} =$
$12 ÷ \frac{1}{2} =$
$\frac{8}{15} ÷ \frac{1}{5} =$
$\frac{5}{9} ÷ \frac{5}{3} =$
$1 - \frac{11}{12} =$
$\frac{7}{8} × \frac{5}{14} =$
$\frac{7}{12} ÷ \frac{7}{4} =$
$\frac{7}{20} ÷ \frac{7}{10} =$
$\frac{3}{8} + \frac{3}{4} =$
$\frac{7}{15} ÷ \frac{7}{10} =$
$\frac{1}{2} ÷ \frac{3}{4} =$
$\frac{2}{3} × 0.9 =$
$\frac{1}{2} × \frac{3}{10} =$

1.$\frac{10}{3}$ 2.$12$ 3.$\frac{21}{4}$ 4.$\frac{1}{7}$ 5.$6$ 6.$16$ 7.$\frac{16}{125}$ 8.$\frac{3}{20}$ 9.$\frac{22}{9}$ 10.$24$ 11.$\frac{8}{3}$ 12.$\frac{1}{3}$ 13.$\frac{1}{12}$ 14.$\frac{5}{16}$ 15.$\frac{1}{3}$ 16.$\frac{1}{2}$ 17.$\frac{9}{8}$ 18.$\frac{2}{3}$ 19.$\frac{2}{3}$ 20.$\frac{3}{5}$ 21.$\frac{3}{20}$

二、计算下面各题，能用简便算法的就用简便算法。
$(\frac{2}{9} + \frac{1}{13}) × 9 × 13$
$\frac{7}{18} ÷ 20 + \frac{1}{20} × \frac{11}{18}$
$\frac{9}{20} ÷ [\frac{1}{4} × (\frac{6}{5} - \frac{3}{10})]$
$\frac{2}{7} + \frac{15}{16} ÷ \frac{3}{2} + \frac{3}{8}$
$(\frac{3}{5} + \frac{3}{5} × 99) ÷ \frac{12}{17}$
$\frac{2}{3} × [(\frac{3}{7} - \frac{3}{10}) ÷ \frac{1}{10}]$

1.$35$ 2.$\frac{1}{20}$ 3.$2$ 4.$1\frac{2}{7}$ 5.$85$ 6.$\frac{6}{7}$