1999+1998+1997+6简算

问题描述:

1999+1998+1997+6简算

1999+1998+1997+6
=(1999+1)+(1998+2)+(1997+3)
=2000+2000+2000
=6000871-(471-276)简算871-(471-276)=871-471+276=400+276=676