1 直接写出得数。(每题1分,共20分)
$\frac {1}{3}+\frac {2}{3}= $ $\frac {1}{2}+\frac {1}{2}= $ $1-\frac {5}{6}= $ $\frac {5}{6}-\frac {5}{6}= $
$\frac {4}{5}-\frac {1}{5}= $ $1-\frac {1}{2}= $ $\frac {1}{5}+\frac {1}{5}= $ $\frac {3}{8}+\frac {3}{8}= $
$\frac {2}{9}+\frac {1}{9}= $ $\frac {6}{7}-\frac {2}{7}= $ $\frac {3}{4}+\frac {1}{4}= $ $\frac {3}{9}+\frac {1}{9}= $
$\frac {3}{5}-\frac {3}{5}= $ $\frac {5}{7}-\frac {3}{7}= $ $\frac {5}{7}+\frac {4}{7}= $ $\frac {7}{8}-\frac {3}{8}= $
$\frac {5}{14}+\frac {3}{14}= $ $1-\frac {3}{13}= $ $\frac {8}{9}-\frac {4}{9}= $ $\frac {17}{20}-\frac {3}{20}= $

1 1 $\frac{1}{6}$ 0
$\frac{3}{5}$ $\frac{1}{2}$ $\frac{2}{5}$ $\frac{3}{4}$
$\frac{1}{3}$ $\frac{4}{7}$ 1 $\frac{4}{9}$
0 $\frac{2}{7}$ $\frac{9}{7}$ $\frac{1}{2}$
$\frac{4}{7}$ $\frac{10}{13}$ $\frac{4}{9}$ $\frac{7}{10}$

2 计算下列各题,能简算的要简算。(每题3分,共18分)
$7-\frac {3}{7}-\frac {4}{7}$ $\frac {3}{5}-(\frac {2}{15}+\frac {1}{3})$ $\frac {5}{6}-\frac {1}{4}-\frac {1}{3}$
$\frac {13}{17}-(\frac {5}{17}+\frac {1}{10})$ $\frac {7}{8}-(\frac {7}{10}-\frac {1}{8})$ $\frac {1}{5}+\frac {1}{2}+\frac {1}{3}$

6 $\frac{2}{15}$ $\frac{1}{4}$
$\frac{63}{170}$ $\frac{3}{10}$ $\frac{31}{30}$

3 解方程。(每题4分,共12分)
$x-\frac {5}{7}= \frac {4}{5}$ $\frac {2}{3}+x= \frac {8}{9}-\frac {1}{6}$ $\frac {3}{4}+x= \frac {17}{20}$

解：x = $\frac{53}{35}$ 解：x = $\frac{-1}{18}$ 解：x = $\frac{-1}{10}$