1又1/3+7/12-9/20+11/30-13/42=4/3+7/12-9/20+11/30-13/42=16/12+7/12-27/60+22/60-13/42=23/12-5/60-13/42=23/12-1/12-13/42=11/贺旁6-13/42=77/42-13/孝埋42=32/21满巧拍蚂意请采纳,不懂可追问
=(拆项)1+1/3+1/3+1/4-1/4-1/迅慎5+1/5-1/粗败6-1/7=1又2/3-1/岩昌颤7=32/21望采纳