一、口算。
$\frac{3}{4} ÷ 12 =$
$\frac{5}{9} × 36 =$
$\frac{7}{5} - \frac{5}{7} × \frac{7}{5} =$
$\frac{3}{4} × 12 =$
$12 ÷ \frac{4}{9} =$
$17 - \frac{1}{7} - \frac{6}{7} =$
$\frac{8}{9} ÷ \frac{7}{18} =$
$\frac{1}{3} × \frac{5}{6} =$
$21 × \frac{3}{7} - 1.5 =$
$\frac{3}{8} ÷ \frac{3}{16} =$
$\frac{5}{6} × \frac{4}{5} =$
$\frac{9}{10} × \frac{2}{3} ÷ \frac{9}{10} =$
$20 ÷ \frac{10}{11} =$
$0.65 × \frac{6}{13} =$
$\frac{5}{8} × \frac{5}{9} + \frac{3}{8} ÷ \frac{9}{5} =$
$\frac{4}{5} ÷ \frac{1}{4} =$
$\frac{3}{7} ÷ \frac{2}{3} =$
$6 × \frac{1}{6} ÷ 6 × \frac{1}{6} =$
$2.4 × \frac{5}{8} =$
$0.33 × \frac{10}{11} =$
$\frac{2}{5} + \frac{3}{5} ÷ 2 =$

1.$\frac{1}{16}$ 2.20 3.$\frac{2}{5}$ 4.9 5.27 6.16 7.$\frac{16}{7}$ 8.$\frac{5}{18}$ 9.7.5 10.2 11.$\frac{2}{3}$ 12.$\frac{2}{3}$ 13.22 14.0.3 15.$\frac{5}{9}$ 16.$\frac{16}{5}$ 17.$\frac{9}{14}$ 18.$\frac{1}{36}$ 19.1.5 20.0.3 21.$\frac{7}{10}$

二、计算下面各题。
$\frac{7}{10} - (\frac{1}{2} + \frac{2}{5}) × \frac{1}{2}$
$35 ÷ \frac{7}{8} × (1 - \frac{2}{7})$
$6 ÷ [8 × (\frac{1}{6} - \frac{1}{24})]$
$\frac{4}{9} ÷ (\frac{5}{6} - \frac{1}{2}) × \frac{3}{8}$
$\frac{9}{20} ÷ \frac{1}{2} × (\frac{2}{5} + \frac{4}{5})$
$\frac{5}{12} ÷ [(1 - \frac{5}{8}) × \frac{5}{6}]$

1.$\frac{1}{4}$ 2.$\frac{200}{7}$ 3.6 4.$\frac{1}{2}$ 5.$\frac{27}{25}$ 6.$\frac{4}{3}$