1 (七分之五加十三分之三)乘以七减二十一除以十三2 7777X9+1111X373 2010X二千零九分之二千零八

(5/7+3/13)*7-21/13=5+21/13-21/13
7777*9+1111*37=1111*63+1111*37=1111*(63+37)=111100
2010*2008/ 1.
(5/7 + 3/13)*7-21/13
=(5/7 + 3/13 - 3/13)*7
=5 2009=(2009+1)(2009-1)/2009=(2009^2-1)/2009=2009-1/2009

(5/7+3/13)*7-21/13=5+21/13-21/13
7777*9+1111*37=1111*63+1111*37=1111*(63+37)=111100
2010*2008/2009=(2009+1)(2009-1)/2009=(2009^2-1)/2009=2009-1/2009

1、原式＝5 /7 ×7+3/13 ×7-21/13=5+(21/13-21/13)=5;
2、原式＝1111X63+1111X37=1111X(63+37)=111100;
3、原式＝(2009+1)X2008/2009＝2009X2008/2009+1X2008/2009=二千零八又二千零九分之一.

1.
(5/7 + 3/13)*7-21/13
=(5/7 + 3/13 - 3/13)*7
=5