一、口算。
$\frac{5}{6}÷\frac{5}{8}=$
$6÷\frac{4}{5}=$
$\frac{2}{5}÷\frac{1}{5}=$
$\frac{3}{5}×\frac{1}{2}=$
$\frac{1}{2}÷\frac{17}{18}=$
$\frac{1}{3}-\frac{1}{4}=$
$\frac{1}{6}+\frac{5}{9}=$
$\frac{3}{4}×\frac{2}{5}=$
$\frac{6}{7}÷\frac{7}{8}=$
$\frac{7}{12}÷\frac{7}{6}=$
$\frac{5}{7}÷2=$
$\frac{1}{9}÷\frac{1}{3}=$
$\frac{2}{7}×1.4=$
$\frac{4}{5}÷\frac{5}{4}=$
$\frac{8}{9}-\frac{3}{4}=$
$\frac{8}{9}×\frac{3}{4}=$
$\frac{1}{2}+\frac{5}{8}=$
$\frac{3}{14}÷\frac{6}{7}=$
$3÷\frac{3}{7}=$
$\frac{3}{8}×\frac{7}{12}=$
$10÷\frac{5}{9}=$

$\frac{4}{3}$
$\frac{15}{2}$
$2$
$\frac{3}{10}$
$\frac{9}{17}$
$\frac{1}{12}$
$\frac{13}{18}$
$\frac{3}{10}$
$\frac{48}{49}$
$\frac{1}{2}$
$\frac{5}{14}$
$\frac{1}{3}$
$\frac{2}{5}$
$\frac{16}{25}$
$\frac{5}{36}$
$\frac{2}{3}$
$\frac{9}{8}$
$\frac{1}{4}$
$7$
$\frac{7}{32}$
$18$

二、计算下面各题，能用简便算法的就用简便算法。
$\frac{11}{27} × \frac{53}{42} × \frac{54}{11}$
$( \frac{2}{7} + \frac{1}{9} ) × 63$
$8.8 × \frac{4}{5} + 1.2 × \frac{4}{5}$
$\frac{8}{17} ÷ 23 + \frac{1}{23} × \frac{9}{17}$
$( \frac{7}{12} + \frac{5}{18} ) ÷ \frac{35}{36}$
$12 - \frac{6}{13} ÷ \frac{9}{26} - \frac{2}{3}$

$\frac{53}{21}$
$25$
$8$
$\frac{1}{23}$
$\frac{31}{35}$
$10$