(1)直接写出得数。
$1-\frac{2}{5}=$
$\frac{1}{3}+\frac{1}{9}=$
$\frac{3}{5}-\frac{1}{4}=$
$\frac{1}{9}+\frac{8}{15}+\frac{8}{9}=$
$\frac{11}{21}+\frac{4}{7}=$
$\frac{7}{10}-\frac{1}{5}=$
$\frac{7}{6}+\frac{7}{6}=$
$\frac{15}{11}-\frac{3}{8}-\frac{5}{8}=$

(1) $\frac{3}{5}$ $\frac{4}{9}$ $\frac{7}{20}$ $1\frac{8}{15}$ $1\frac{2}{21}$ $\frac{1}{2}$ $2\frac{1}{3}$ $\frac{4}{11}$

(2)解下列方程。
$x-\frac{4}{9}=\frac{1}{6}$
$\frac{1}{2}+x=\frac{4}{5}$
$\frac{11}{12}-x=\frac{5}{6}-\frac{3}{4}$
$\frac{6}{7}+x=\frac{20}{21}$
$\frac{15}{26}-x=\frac{1}{2}$
$4\frac{3}{5}+x=6$

(2)$x=\frac{11}{18}$ $x=\frac{3}{10}$ $x=\frac{5}{6}$ $x=\frac{2}{21}$ $x=\frac{1}{13}$ $x=1\frac{2}{5}$

(3)用递等式计算。
$\frac{1}{6}+\frac{1}{5}+\frac{1}{12}$
$\frac{5}{6}-\frac{1}{4}-\frac{1}{3}$
$12.47-\frac{5}{6}+7.53-\frac{7}{6}$
$\frac{3}{5}-(\frac{2}{15}+\frac{1}{3})$
$\frac{5}{9}-(\frac{3}{4}-\frac{1}{2})$
$\frac{5}{12}+\frac{3}{5}+\frac{7}{12}-\frac{2}{5}$

(3)$\frac{9}{20}$ $\frac{1}{4}$ 18 $\frac{2}{15}$ $\frac{11}{36}$ $1\frac{1}{5}$