连加、连减、加减混合 1: 1/2+2/3-3/4 =6/12+8/12-9/12 =5/12 7/8-1/6+1/4 =21/24-4/24+6/24 =23/24 1-(3/4-2/9) =1-(27/36-8/36) =17/369/10-1/5-1/2 =9/10-2/10-5/10 =1/5 1/4+3/7+1/2=7/28+12/28+14/28=33/28 7/8-(2/3+1/6)=21/24-(16/24+4/24)=1/242: 7/8+1/4-1/2 =7/8+2/8-4/8 |