=3/4+2+3/4+1/8-12-5/7-4-1/8
=3+6/4-12-4-5/7
=2/4-5/7-12
=14/28-20/28-12
=-3/14-12
=-12又14分之3
希望能帮你忙,不懂请追问,懂了请采纳,谢谢