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第115页

信息发布者：

$=\frac {10}{12}-\frac {3}{12}+\frac {8}{12}$

$=\frac {5}{4}$

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

$=2+1$

$=3$

$=\frac {13}{6}-\frac {7}{6}-\frac {6}{7}$

$=1-\frac {6}{7}$

$=\frac {1}{7}$

$=(\frac {7}{12}+\frac {5}{12})-(\frac {3}{8}+\frac {1}{8})$

$=1-\frac 12$

$=\frac {1}{2}$

$=20-2\frac {1}{2}-2\frac {1}{4}-2\frac {1}{8}-2\frac {1}{16}-2\frac {1}{32}-2\frac {1}{64}$

$=20-2×6-(\frac {1}{2}+\frac {1}{4}+\frac {1}{8}+\frac {1}{16}+\frac {1}{32}+\frac {1}{64})$

$=8-(1-\frac {1}{64})$

$=7\frac {1}{64}$

$\begin {aligned}解：x&=\frac {3}{7}+\frac {3}{7}\\x &=\frac {6}{7}\end {aligned}$

$\begin {aligned}解：3x+8.5&=10\\3x&=1.5\\x &=0.5\end {aligned}$

$\begin {aligned}解：4.2x&=12.6\\x &=3\end {aligned}$

$\begin {aligned}解：8x&=20.4×2.4\\8x&=48.96\\x &=6.12\end {aligned}$

3.14×6²÷2−3.14×(6÷2)²=28.26(平方厘米)

3.14×4²÷2=25.12(平方厘米)

12.56

$=1-\frac {1}{24}$

$=\frac {23}{24}$