1. 用简便方法计算。
(1) $\frac{2}{9}-\frac{4}{7}+\frac{7}{9}-\frac{3}{7}$
(2) $\frac{7}{9}-\frac{3}{11}-\frac{8}{11}+\frac{2}{9}$
(3) $10-\frac{1}{13}-\frac{12}{13}$
(4) $\frac{5}{7}-\frac{4}{9}+\frac{2}{7}+\frac{5}{9}$

(1)0 (2)0 (3)9 (4)$1\frac {1}{9}$

2. 计算下面各题,怎样简便就怎样算。
(1) $2.75-\frac{12}{25}+2.25-\frac{13}{25}$
(2) $\frac{1}{3}+\frac{1}{4}-\frac{1}{3}+\frac{1}{4}$
(3) $\frac{5}{8}-(\frac{5}{9}-\frac{3}{8})$
(4) $\frac{13}{6}-(\frac{1}{7}+\frac{7}{6})$

(1)4 (2)$\frac {1}{2}$ (3)$\frac {4}{9}$ (4)$\frac {6}{7}$