1. 直接写出得数。
$ \frac{1}{7} + \frac{3}{14} = $$ $$ \frac{3}{5} + \frac{1}{2} = $$ $$ \frac{7}{5} - \frac{4}{9} = $$ $$ \frac{3}{4} + \frac{2}{5} + \frac{1}{4} = $
$ \frac{9}{25} - \frac{1}{10} = $$ $$ \frac{3}{4} + \frac{1}{3} = $$ $$ 5 - \frac{2}{7} = $$ $$ \frac{7}{9} - \frac{1}{2} + \frac{2}{9} = $
$ \frac{7}{15} + \frac{1}{3} = $$ $$ \frac{3}{7} - \frac{1}{4} = $$ $$ \frac{1}{5} + \frac{4}{5} = $$ $$ \frac{2}{5} - \frac{2}{15} + \frac{1}{3} = $
$ \frac{2}{3} - \frac{2}{5} = $$ $$ \frac{5}{6} - \frac{2}{3} = $$ $$ \frac{2}{9} - \frac{2}{15} = $$ $$ \frac{14}{9} - (\frac{2}{3} + \frac{5}{9}) = $
$ \frac{1}{4} + \frac{1}{5} = $$ $$ \frac{2}{5} + \frac{1}{3} = $$ $$ \frac{1}{6} + \frac{8}{9} = $$ $$ \frac{7}{12} + \frac{5}{4} - \frac{5}{6} = $
$ \frac{7}{8} - \frac{1}{7} = $$ $$ \frac{2}{9} + \frac{1}{5} = $$ $$ \frac{9}{10} - \frac{1}{3} = $$ $$ \frac{11}{7} + \frac{5}{3} - \frac{4}{7} = $

1. $\frac{5}{14}$ $\frac{11}{10}$ $\frac{43}{45}$ $1\frac{2}{5}$
$\frac{13}{50}$ $\frac{13}{12}$ $4\frac{5}{7}$ $\frac{1}{2}$
$\frac{4}{5}$ $\frac{5}{28}$ $1$ $\frac{3}{5}$
$\frac{4}{15}$ $\frac{1}{6}$ $\frac{4}{45}$ $\frac{1}{3}$
$\frac{9}{20}$ $\frac{11}{15}$ $\frac{19}{18}$ $1$
$\frac{41}{56}$ $\frac{19}{45}$ $\frac{17}{30}$ $\frac{8}{3}$

2. 解方程。
$ x - \frac{7}{12} = \frac{13}{18} $$ $$ \frac{1}{6} + x = \frac{3}{8} $$ $$ x + \frac{1}{4} + \frac{1}{5} = \frac{3}{4} $
$ \frac{2}{3} - x = \frac{5}{12} $$ $$ 0.25x - \frac{9}{10} = \frac{1}{10} $$ $$ x - (\frac{3}{4} - \frac{2}{5}) = 1 $

2. $x=\frac{47}{36}$ $x=\frac{5}{24}$ $x=\frac{3}{10}$
$x=\frac{1}{4}$ $x=4$ $x=\frac{27}{20}$

一瓶果汁连瓶重$$ \frac{5}{2} $$千克，喝了一半果汁后连瓶重$$ \frac{7}{4} $$千克，空瓶重多少千克？

思维提升
$\frac{5}{2}-\frac{7}{4}=\frac{3}{4}$（千克）
$\frac{7}{4}-\frac{3}{4}=1$（千克）