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

$\frac{1}{3} + \frac{1}{3} = \frac{2}{3}$
$\frac{2}{5} + \frac{3}{5} = 1$
$\frac{4}{8} + \frac{2}{8} = \frac{6}{8}$
$\frac{7}{10} + \frac{3}{10} = 1$
$1 - \frac{1}{4} = \frac{3}{4}$
$\frac{8}{9} - \frac{2}{9} = \frac{6}{9}$
$\frac{5}{6} - \frac{3}{6} = \frac{2}{6}$
$1 - \frac{4}{7} = \frac{3}{7}$

4. 在○里填上“＞”“＜”或“=”。
$\frac{2}{3} ◯ \frac{1}{3}$
$\frac{2}{7} ◯ \frac{5}{7}$
$\frac{5}{5} ◯ 1$
$\frac{1}{5} ◯ 1-\frac{4}{5}$
$1-\frac{1}{9} ◯ \frac{4}{9}$
$\frac{6}{8}-\frac{1}{8} ◯ \frac{2}{8}+\frac{4}{8}$
$\frac{6}{7}-\frac{3}{7} ◯ \frac{2}{7}$
$1 ◯ \frac{2}{7}+\frac{3}{7}$
$1-\frac{5}{6} ◯ 1-\frac{3}{6}$

$\frac{2}{3} ＞ \frac{1}{3}$
$\frac{2}{7} ＜ \frac{5}{7}$
$\frac{5}{5} = 1$
$\frac{1}{5} = 1-\frac{4}{5}$
$1-\frac{1}{9} ＞ \frac{4}{9}$
$\frac{6}{8}-\frac{1}{8} ＜ \frac{2}{8}+\frac{4}{8}$
$\frac{6}{7}-\frac{3}{7} ＞ \frac{2}{7}$
$1 ＞ \frac{2}{7}+\frac{3}{7}$
$1-\frac{5}{6} ＜ 1-\frac{3}{6}$