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第74页

信息发布者：

$=\frac {1}{24}+\frac {3}{4}$

$=\frac {19}{24}$

$=\frac {7}{8}-\frac {3}{10}$

$=\frac {23}{40}$

$=\frac {7}{24}+\frac {3}{4}$

$=\frac {25}{24}$

$=\frac {4}{3}-\frac {3}{4}$

$=\frac {7}{12}$

$\begin {aligned}解：x&=\frac {2}{3}+\frac {1}{3}\\x &=1\end {aligned}$

$\begin {aligned}解：4x&=1\\x &=0.25\end {aligned}$

$\begin {aligned}解：x&=\frac {1}{4}+\frac {2}{7}-\frac {3}{14}\\x &=\frac {15}{28}-\frac {3}{14}\\x &=\frac {9}{28}\end {aligned}$

$\begin {aligned}解：x&=\frac {4}{5}-\frac {1}{5}\\x &=\frac {3}{5}\end {aligned}$

$\frac {2}{5}$ + $\frac {1}{4}$ + $\frac {1}{4}$=$\frac {9}{10}$ (米)

答：周长是$\frac {9}{10}$米。

$\frac {3}{4}$-$\frac {1}{3}$ + $\frac {3}{4}$=$\frac {7}{6}$ (吨)

答：一共$\frac {7}{6}$吨。

$\frac {1}{3}$ + $\frac {1}{9}$ + $\frac {1}{3}$=$\frac {7}{9}$

答：一共看了全书的$\frac {7}{9}。$