1 11x13x10x(3/11-1/13)-120 =11x13x10x3/11-11x13x10x1/13-120=390-110-120=160.2 (2890+5/6+7/8+7/10)/(5/6+7/8+7/10)=2890/(5/6+7/8+7/10)+1=2890/[(5*20+7*15+7*12)/120+1=1200+1`=12013 1/2+1/6+1/12+1/20+1/30...第2题没懂起(2890+5/6+7/8+7/10)/(5/6+7/8+7/10)= [2890+(5/6+7/8+7/10))/(5/6+7/8+7/10)=2890/(5/6+7/8+7/10)+1=[2890/(289/120)]+1=1200+1=1201