第18页 - 启东中学作业本七年级数学人教版

C

B

5

0

$=(7-7)+(23-21)$

$=0+2$

$=2$

$=(12-12)+(11-8-2)$

$=0+1$

$=1$

$=\frac {1}{8}+2 \frac {1}{4}-2 \frac {1}{8}-\frac {1}{4}$

$=-(2 \frac {1}{8}-\frac {1}{8})+(2 \frac {1}{4}-\frac {1}{4})$

$=-2+2$

$=0$

$=-(13 \frac {1}{5}-4 \frac {1}{5})+(\frac {5}{6}-\frac {5}{6})$

$=-9+0$

$=-9$

$=-2\frac {1}{3}+(-0.5)+\frac {1}{3}$

$=-2+(-0.5)$

$= -2.5$

$=(3\frac {1}{4}+5\frac {3}{4})-(2\frac {3}{5}+8\frac {2}{5})$

$=9-11$

$=-2$

$=[\frac {1}{8}+(-3\frac {1}{8})]+(3\frac {1}{4}-\frac {1}{4})+11\frac {2}{3}$

$= -3+3+11\frac {2}{3}$

$=11\frac {2}{3}$