【参考答案】
1、原式=29×(-12)+(3/4)×(-12)+290
=-348-9+290
=-357+290
=-67
2、原式=13×(2/3)-(5/7)×(7/20)-(1/3)×(-13)-(2/7)×(7/20)
=13×(2/3)+(1/3)×13-(7/20)×[(5/7)+(2/7)]
=(1/3)×(26+13)-(7/20)
=13-(7/20)
=253/20
3、原式=(1/3)[1-(1/4)]+(1/3)[(1/4)-(1/7)]+(1/3)[(1/7)-(1/10)]+……+(1/3)[(1/2008)-(1/2011)]
=(1/3)[1-(1/4)+(1/4)-(1/7)+(1/7)-(1/10)+……+(1/2008)-(1/2011)]
=(1/3)×[1-(1/2011)]
=(1/3)×(2010/2011)
=670/2011
有不理解的地方欢迎追问.