一、口算。
$\frac{3}{4} + \frac{2}{5} =$
$20 × \frac{5}{12} =$
$\frac{1}{7} + \frac{6}{7} × 7 =$
$\frac{3}{10} ÷ \frac{1}{10} =$
$3.6 × \frac{4}{9} =$
$\frac{1}{3} × 9 × \frac{2}{3} =$
$\frac{3}{5} ÷ \frac{4}{5} =$
$\frac{5}{8} × \frac{2}{15} =$
$\frac{2}{5} + \frac{3}{7} + \frac{3}{5} =$
$\frac{2}{3} × 0.03 =$
$\frac{9}{28} ÷ \frac{11}{12} =$
$48 × ( \frac{3}{4} - \frac{1}{2} ) =$
$\frac{1}{4} ÷ \frac{3}{4} =$
$\frac{7}{16} - \frac{1}{4} =$
$\frac{1}{2} × \frac{4}{5} × \frac{1}{2} =$
$\frac{3}{8} × \frac{4}{7} =$
$\frac{8}{13} ÷ \frac{6}{13} =$
$\frac{1}{4} × 8.5 × 4 =$
$\frac{15}{28} ÷ \frac{2}{7} =$
$\frac{2}{13} × \frac{3}{4} =$
$( \frac{9}{10} - \frac{2}{5} ) ÷ 4 =$

1.$\frac{23}{20}$ 2.$\frac{25}{3}$ 3.$6\frac{1}{7}$ 4.3 5.1.6 6.2 7.$\frac{3}{4}$ 8.$\frac{1}{12}$ 9.$1\frac{3}{7}$ 10.0.02 11.$\frac{27}{77}$ 12.12 13.$\frac{1}{3}$ 14.$\frac{3}{16}$ 15.$\frac{1}{5}$ 16.$\frac{3}{14}$ 17.$\frac{4}{3}$ 18.8.5 19.$\frac{15}{8}$ 20.$\frac{3}{26}$ 21.$\frac{1}{8}$

二、计算下面各题，能用简便算法的就用简便算法。
$\frac{7}{9} ÷ \frac{13}{7} + \frac{2}{9} × \frac{7}{13}$
$5 × \frac{1}{5} ÷ 5 × \frac{4}{5}$
$\frac{7}{8} ÷ 7 + 1.5 ÷ (0.5 - \frac{1}{3})$
$\frac{7}{2} × \frac{5}{8} - \frac{3}{2} ÷ \frac{8}{5}$
$1 - \frac{5}{8} ÷ \frac{25}{28} - \frac{3}{10}$
$\frac{3}{4} × \frac{1}{6} + \frac{5}{6} × 0.75$

1.$\frac{7}{13}$ 2.$\frac{4}{25}$ 3.$9\frac{1}{8}$ 4.$\frac{5}{4}$ 5.0 6.$\frac{3}{4}$