四、我会判断并改正。
1. $\frac{5}{8}-(\frac{1}{2}-\frac{1}{9})$ 改正：
$=\frac{5}{8}-\frac{1}{2}-\frac{1}{9}$
$=\frac{1}{8}-\frac{1}{9}$
$=\frac{1}{72}$()
2. $\frac{7}{10}-\frac{2}{5}-\frac{2}{15}$ 改正：
$=\frac{7}{10}-(\frac{2}{5}-\frac{2}{15})$
$=\frac{7}{10}-\frac{4}{15}$
$=\frac{13}{30}$()

1. × $\frac{5}{8}-(\frac{1}{2}-\frac{1}{9})=\frac{5}{8}-\frac{1}{2}+\frac{1}{9}=\frac{17}{72}$
2. × $\frac{7}{10}-\frac{2}{5}-\frac{2}{15}=\frac{7}{10}-(\frac{2}{5}+\frac{2}{15})=\frac{1}{6}$

五、我会算。（能简算的要简算）
$\frac{5}{6}+\frac{3}{4}-\frac{2}{3}$ $\frac{7}{10}-(\frac{1}{5}+\frac{1}{6})$ $1-\frac{7}{22}+\frac{4}{11}$
$\frac{5}{9}-(\frac{1}{3}-\frac{5}{18})$ $2+\frac{9}{14}+\frac{5}{14}$ $\frac{11}{20}+\frac{4}{9}+\frac{9}{20}$
$\frac{6}{7}-(\frac{4}{7}+\frac{1}{14})$ $\frac{7}{20}-\frac{1}{3}+\frac{3}{20}$ $\frac{4}{5}-(\frac{5}{6}-\frac{1}{3})$

$\frac{11}{12}$ $\frac{1}{3}$ $1\frac{1}{22}$ $\frac{1}{2}$ $3$ $1\frac{4}{9}$ $\frac{3}{14}$ $\frac{1}{6}$ $\frac{3}{10}$

1. $\frac{5}{6}$与$\frac{7}{18}$的差比$\frac{1}{2}$与$\frac{4}{9}$的和少多少？

1. $\frac{1}{2}$

2. $\frac{2}{5}$比$\frac{7}{8}$与$\frac{1}{2}$的和少多少？

2. $\frac{39}{40}$