1. 直接写出得数。
$\frac {7}{8}+\frac {11}{8}=$
$\frac {13}{15}-\frac {3}{15}=$
$2-\frac {5}{12}=$
$\frac {5}{6}+\frac {11}{24}=$

$\frac{7}{8}+\frac{11}{8}=\frac{7+11}{8}=\frac{18}{8}=\frac{9}{4}$
$\frac{13}{15}-\frac{3}{15}=\frac{13-3}{15}=\frac{10}{15}=\frac{2}{3}$
$2-\frac{5}{12}=\frac{24}{12}-\frac{5}{12}=\frac{19}{12}$
$\frac{5}{6}+\frac{11}{24}=\frac{20}{24}+\frac{11}{24}=\frac{31}{24}$

2. 计算下面各题。
$\frac {3}{5}+\frac {5}{8}$
$\frac {7}{12}-\frac {4}{9}$
$\frac {1}{6}+\frac {7}{20}$
$\frac {9}{10}-\frac {3}{8}$
$\frac {2}{3}+\frac {3}{8}$
$\frac {7}{15}-\frac {2}{9}$
$\frac {5}{12}+\frac {5}{8}$
$\frac {7}{6}-\frac {3}{4}$

$\frac{3}{5}+\frac{5}{8}$
$=\frac{24}{40}+\frac{25}{40}$
$=\frac{49}{40}$
$\frac{7}{12}-\frac{4}{9}$
$=\frac{21}{36}-\frac{16}{36}$
$=\frac{5}{36}$
$\frac{1}{6}+\frac{7}{20}$
$=\frac{10}{60}+\frac{21}{60}$
$=\frac{31}{60}$
$\frac{9}{10}-\frac{3}{8}$
$=\frac{36}{40}-\frac{15}{40}$
$=\frac{21}{40}$
$\frac{2}{3}+\frac{3}{8}$
$=\frac{16}{24}+\frac{9}{24}$
$=\frac{25}{24}$
$\frac{7}{15}-\frac{2}{9}$
$=\frac{21}{45}-\frac{10}{45}$
$=\frac{11}{45}$
$\frac{5}{12}+\frac{5}{8}$
$=\frac{10}{24}+\frac{15}{24}$
$=\frac{25}{24}$
$\frac{7}{6}-\frac{3}{4}$
$=\frac{14}{12}-\frac{9}{12}$
$=\frac{5}{12}$

3. 下面各题，能简算的要简算。
$\frac {2}{3}+\frac {3}{4}+\frac {1}{6}$
$\frac {14}{15}-\frac {1}{3}-\frac {3}{5}$
$\frac {7}{12}-\frac {2}{5}+\frac {5}{12}$
$\frac {7}{8}-(\frac {2}{5}+\frac {3}{8})$
$\frac {2}{9}+\frac {5}{6}-\frac {2}{9}+\frac {5}{6}$
$1-\frac {1}{7}-\frac {5}{7}$

$\frac{2}{3}+\frac{3}{4}+\frac{1}{6}$
$=\frac{8}{12}+\frac{9}{12}+\frac{2}{12}$
$=\frac{19}{12}$
$\frac{14}{15}-\frac{1}{3}-\frac{3}{5}$
$=\frac{14}{15}-\frac{5}{15}-\frac{9}{15}$
$=0$
$\frac{7}{12}-\frac{2}{5}+\frac{5}{12}$
$=\frac{7}{12}+\frac{5}{12}-\frac{2}{5}$
$=1-\frac{2}{5}$
$=\frac{3}{5}$
$\frac{7}{8}-(\frac{2}{5}+\frac{3}{8})$
$=\frac{7}{8}-\frac{3}{8}-\frac{2}{5}$
$=\frac{1}{2}-\frac{2}{5}$
$=\frac{5}{10}-\frac{4}{10}$
$=\frac{1}{10}$
$\frac{2}{9}+\frac{5}{6}-\frac{2}{9}+\frac{5}{6}$
$=\frac{2}{9}-\frac{2}{9}+\frac{5}{6}+\frac{5}{6}$
$=0+\frac{10}{6}$
$=\frac{5}{3}$
$1-\frac{1}{7}-\frac{5}{7}$
$=1-(\frac{1}{7}+\frac{5}{7})$
$=1-\frac{6}{7}$
$=\frac{1}{7}$

如图，长方形的面积是 96 平方厘米，a 是长方形长的$\frac {1}{2}$，b 是长方形宽的$\frac {1}{3}$。涂色部分的面积占长方形面积的几分之几？

$\frac{1}{3}×\frac{1}{2}=\frac{1}{6}$
$\frac{1}{2}×\frac{1}{2}=\frac{1}{4}$
$\frac{1}{6}+\frac{1}{4}=\frac{5}{12}$
$1-\frac{5}{12}=\frac{7}{12}$
答：涂色部分的面积占长方形面积的$\frac{7}{12}$。