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第79页

信息发布者：

A

C

A

$=\frac {12}{7}-(\frac {5}{7}+\frac {4}{5})$

$=\frac {12}{7}-\frac {5}{7}-\frac {4}{5}$

$=1-\frac {4}{5}$

$=\frac{1}{5}$

$=\frac{3}{7}×(\frac {9}{5}-\frac {4}{5})$

$=\frac {3}{7}×1$

$=\frac {3}{7}$

$=\frac{2}{23}×23+\frac{46}{71}+\frac{25}{71}$

$=2+(\frac {46}{71}+\frac {25}{71})$

$=2+1$

$=3$

$=(46+1)×\frac{13}{46}$

$=46×\frac{13}{46}+\frac {13}{46}$

$=13+\frac {13}{46}$

$=13\frac{13}{46}$

$解:\frac{1}{12}x=12$

$x=144$

$解:\frac {2}{5}x-\frac {3}{8}=\frac {5}{8}$

$\frac {2}{5}x=\frac {3}{8}+\frac {5}{8}$

$\frac {2}{5}x=1$

$x=\frac {5}{2}$

$240×(1-\frac{2}{5})=144(千克)$

$320×(1+\frac{5}{16})=420(人)$

9

4

B

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